Semiconductor devices and methods of manufacturing the same

ABSTRACT

A semiconductor device may include a first active fin, a plurality of second active fins, a first source/drain layer structure, and a second source/drain layer structure. The first active fin may be on a first region of a substrate. The second active fins may be on a second region of the substrate. The first and second gate structures may be on the first and second active fins, respectively. The first source/drain layer structure may be on a portion of the first active fin that is adjacent to the first gate structure. The second source/drain layer structure may commonly contact upper surfaces of the second active fins adjacent to the second gate structure. A top surface of the second source/drain layer structure may be further from the surface of the substrate than a top surface of the first source/drain layer structure is to the surface of the substrate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/388,347 filed Apr. 18, 2019, which application is a continuation ofU.S. patent application Ser. No. 15/351,739, filed Nov. 15, 2016, whichitself claims priority under 35 U.S.C. § 119 to Korean PatentApplication No. 10-2015-0163323, filed on Nov. 20, 2015 in the KoreanIntellectual Property Office (KIPO), the contents of which are herebyincorporated herein by reference in their entirety.

BACKGROUND 1. Field

Example embodiments of the inventive concepts relate to semiconductordevices, and more particularly, to semiconductor devices includingepitaxial layers and methods of manufacturing the same.

2. Description of the Related Art

In a fin-based field effect transistor (finFET), a source/drain layermay be formed on an active fin by a selective epitaxial growth (SEG)process. The source/drain layer may grow both in vertical and horizontaldirections, and when the active fins are close to each other, thesource/drain layers grown from the active fins, respectively, may bemerged with each other. In a static random access memory (SRAM) device,when the source/drain layers grown from the active fins of neighboringtransistors are merged with each other, an electric failure may occur.

SUMMARY

The inventive concepts provide semiconductor devices having goodcharacteristics and methods of manufacturing semiconductor deviceshaving good characteristics.

According to some embodiments of the inventive concepts, semiconductordevices are provided. A semiconductor device may include a first activefin, a plurality of second active fins, a first source/drain layerstructure, and a second source/drain layer structure. The first activefin may be on a first region of a surface of a substrate. The surface ofthe substrate may include the first region and a second region. Thesecond active fins may be on the second region of the substrate. Thefirst and second gate structures may be on the first and second activefins, respectively. The first source/drain layer structure may be on aportion of the first active fin that is adjacent to the first gatestructure. The second source/drain layer structure may commonly contactupper surfaces of the second active fins adjacent to the second gatestructure, and a top surface of the second source/drain layer structuremay be further from the surface of the substrate than a top surface ofthe first source/drain layer structure is to the surface of thesubstrate.

In some embodiments, the first source/drain layer structure may includea first semiconductor layer on the first active fin, a secondsemiconductor layer on the first semiconductor layer, and a thirdsemiconductor layer on the second semiconductor layer. The secondsource/drain layer structure may include fourth semiconductor layers onthe respective second active fins that are spaced apart from each other,a continuous fifth semiconductor layer commonly on the fourthsemiconductor layers, and a continuous sixth semiconductor layer on thefifth semiconductor layer.

In some embodiments, the first and fourth semiconductor layers mayinclude silicon-germanium with a first germanium concentration, thesecond and fifth semiconductor layers may include silicon-germanium witha second germanium concentration greater than the first germaniumconcentration, and the third and sixth semiconductor layers may includesilicon-germanium with a third germanium concentration greater than thesecond germanium concentration.

In some embodiments, the first and fourth semiconductor layers mayfurther include p-type impurities with a fourth impurity concentration,the second and fifth semiconductor layers may further include p-typeimpurities with a fifth impurity concentration greater than the fourthimpurity concentration, and the third and sixth semiconductor layers mayfurther include p-type impurities with a sixth impurity concentrationgreater than the fifth impurity concentration.

In some embodiments, the first and fourth semiconductor layers mayinclude silicon carbide with a first carbon concentration, the secondand fifth semiconductor layers may include silicon carbide with a secondcarbon concentration greater than the first carbon concentration, andthe third and sixth semiconductor layers may include silicon carbidewith a third carbon concentration greater than the second carbonconcentration.

In some embodiments, the first and fourth semiconductor layers mayfurther include n-type impurities with a fourth impurity concentration,the second and fifth semiconductor layers may further include n-typeimpurities with a fifth impurity concentration greater than the fourthimpurity concentration, and the third and sixth semiconductor layers mayfurther include n-type impurities with a sixth impurity concentrationgreater than the fifth impurity concentration.

In some embodiments, the first and second active fins may includerespective longest dimensions that extend in a first directionsubstantially parallel to the surface of the substrate, and the firstand second gate structures may include respective longest dimensionsthat extend in a second direction that is substantially parallel to thesurface of the substrate and crosses the first direction.

In some embodiments, a cross-section of the second semiconductor layertaken along the second direction may have a first shape including uppersidewall surfaces defining an angle with respect to the surface of thesubstrate and facing away from the substrate, lower sidewall surfacesdefining an angle with respect to the surface of the substrate andfacing towards the surface of the substrate, and a top surface that isparallel to the surface of the substrate. The third semiconductor layermay be formed on the upper sidewall surfaces of the second semiconductorlayer. A cross-section of the fifth semiconductor layer taken along thesecond direction may have a shape including a plurality of second shapesthat are connected to each other in the second direction. The secondshapes may be on respective ones of the second active fins and mayinclude upper sidewall surfaces defining an angle with respect to thesurface of the substrate and facing away from the substrate and lowersidewall surfaces defining an angle with respect to the surface of thesubstrate and facing towards the surface of the substrate. The sixthsemiconductor layer may be formed on the upper sidewall surfaces of thefifth semiconductor layer.

In some embodiments, a top surface of the sixth semiconductor layer maybe substantially coplanar with a top surface of the fifth semiconductorlayer.

In some embodiments, a cross-section of the sixth semiconductor layertaken along the second direction may include a top surface that issubstantially flat and substantially parallel to the surface of thesubstrate along the second direction.

In some embodiments, in a cross-section taken along the seconddirection, a thickness of the sixth semiconductor layer on outer ones ofthe upper sidewall surfaces of outermost ones of the second shapes ofthe fifth semiconductor layer may be less than a thickness of the sixthsemiconductor layer on inner ones of the upper sidewall surfaces of theoutermost ones of the second shapes of the fifth semiconductor layer andless than thicknesses of the sixth semiconductor layer on upper sidewallsurfaces of inner ones of the second shapes of the fifth semiconductorlayer.

In some embodiments, in a cross-section taken along the seconddirection, a thickness of the third semiconductor layer on uppersidewall surfaces of the second semiconductor layer may be less than athickness of the sixth semiconductor layer on inner ones of the uppersidewall surfaces of outermost ones of the second shapes of the fifthsemiconductor layer and less than thicknesses of the sixth semiconductorlayer on upper sidewall surfaces of inner ones of the second shapes ofthe fifth semiconductor layer.

In some embodiments, a cross-section of the second semiconductor layertaken along the second direction may have a first shape including uppersidewall surfaces defining an angle with respect to the surface of thesubstrate and facing away from the substrate and lower sidewall surfacesdefining an angle with respect to the surface of the substrate andfacing towards the surface of the substrate. The third semiconductorlayer may be formed on the upper sidewall surfaces of the secondsemiconductor layer. A cross-section of the fifth semiconductor layertaken along the second direction may have a shape including a pluralityof second shapes that are connected to each other in the seconddirection. The second shapes may be on respective ones of the secondactive fins and may include upper sidewall surfaces defining an anglewith respect to the surface of the substrate and facing away from thesubstrate and lower sidewall surfaces defining an angle with respect tothe surface of the substrate and facing towards the surface of thesubstrate. The sixth semiconductor layer may be formed on the uppersidewall surfaces of the fifth semiconductor layer.

In some embodiments, a top surface of the sixth semiconductor layer maybe farther from the surface of the substrate than a top surface of thefifth semiconductor layer is to the surface of the substrate.

In some embodiments, a cross-section of the sixth semiconductor layertaken along the second direction may include a central top surface thatis substantially flat and substantially parallel to the surface of thesubstrate along the second direction.

In some embodiments, in a cross-section taken along the seconddirection, a thickness of the sixth semiconductor layer on outer ones ofthe upper sidewall surfaces of outermost ones of the second shapes ofthe fifth semiconductor layer may be less than a thickness of the sixthsemiconductor layer on inner ones of the upper sidewall surfaces of theoutermost ones of the second shapes of the fifth semiconductor layer andless than thicknesses of the sixth semiconductor layer on upper sidewallsurfaces of inner ones of the second shapes of the fifth semiconductorlayer.

In some embodiments, in a cross-section taken along the seconddirection, a thickness of the third semiconductor layer on uppersidewall surfaces of the second semiconductor layer may be less than athickness of the sixth semiconductor layer on inner ones of the uppersidewall surfaces of outermost ones of the second shapes of the fifthsemiconductor layer and less than thicknesses of the sixth semiconductorlayer on upper sidewall surfaces of inner ones of the second shapes ofthe fifth semiconductor layer.

In some embodiments, the first source/drain layer structure may includea first silicon layer at least partially covering the second and thirdsemiconductor layers, and the second source/drain layer structure mayinclude a second silicon layer at least partially covering the fifth andsixth semiconductor layers.

In some embodiments, the semiconductor device further include a firstcontact plug on the first source/drain layer structure, and a secondcontact plug on the second source/drain layer structure.

In some embodiments, a first length of the first contact plug in avertical direction that is substantially perpendicular to the surface ofthe substrate may be greater than a second length of the second contactplug in the vertical direction.

In some embodiments, a top surface of the first contact plug may besubstantially coplanar with a top surface of the second contact plug,and a bottom of the first contact plug may be closer to the surface ofthe substrate than a bottom of the second contact plug is to the surfaceof the substrate.

In some embodiments, bottoms of the first and second contact plugs maybe substantially flat and substantially parallel to the surface of thesubstrate.

In some embodiments, the bottom of the first contact plug may have acentral portion that is farther from the surface of the substrate thanedge portions thereof are to the surface of the substrate, and thebottom of the second contact plug may have a flat central portion thatis farther from the surface of the substrate than edge portions thereofare to the surface of the substrate.

In some embodiments, the semiconductor device may further include afirst metal silicide pattern between the first source/drain layerstructure and the first contact plug, and a second metal silicidepattern between the second source/drain layer structure and the secondcontact plug.

In some embodiments, the first active fin may include a plurality offirst active fins, and the first source/drain layer structure mayinclude a plurality of structures that are spaced apart from each otherwith ones of the plurality of structures on respective ones of theplurality of first active fins.

In some embodiments, the first region may be a static random accessmemory (SRAM) region including an SRAM device, and the second region maybe a logic region including a logic device.

According to some embodiments of the inventive concepts, semiconductordevices are provided. A semiconductor device may include a first activefin, a plurality of second active fins, first and second gatestructures, a second source/drain layer structure, a first contact plug,and a second contact plug. The first active fin may be on a first regionof a surface of a substrate, and the surface of the substrate mayinclude the first region and a second region. The second active fins maybe formed on the second region of the substrate. The first and secondgate structures may be formed on the first and second active fins,respectively. The first source/drain layer structure may be formed onthe first active fin adjacent the first gate structure. The secondsource/drain layer structure may commonly contact upper surfaces of thesecond active fins adjacent the second gate structure and a top surfaceof the second source/drain layer structure may be substantially coplanarwith a top surface of the first source/drain layer structure. The firstcontact plug may be formed on the first source/drain layer structure.The second contact plug may be formed on the second source/drain layerstructure, and a bottom of the second contact plug may be substantiallyflat and substantially parallel to the surface of the substrate.

In some embodiments, the first source/drain layer structure may includea first semiconductor layer on the first active fin, a secondsemiconductor layer on the first semiconductor layer, and a thirdsemiconductor layer on the second semiconductor layer. The secondsource/drain layer structure may include fourth semiconductor layers onthe respective second active fins that are spaced apart from each other,a continuous fifth semiconductor layer commonly on the fourthsemiconductor layers, and a continuous sixth semiconductor layer on thefifth semiconductor layer.

In some embodiments, the first and fourth semiconductor layers mayinclude silicon-germanium with a first germanium concentration, thesecond and fifth semiconductor layers may include silicon-germanium witha second germanium concentration greater than the first germaniumconcentration, and the third and sixth semiconductor layers may includesilicon-germanium with a third germanium concentration greater than thesecond germanium concentration.

In some embodiments, the first and second active fins may includerespective longest dimensions that extend in a first directionsubstantially parallel to the surface of the substrate, and the firstand second gate structures may include respective longest dimensionsthat extend in a second direction that is substantially parallel to thesurface of the substrate and crosses the first direction.

In some embodiments, a cross-section of the second semiconductor layertaken along the second direction may have a first shape that includesupper sidewall surfaces defining an angle with respect to the surface ofthe substrate and facing away from the substrate, lower sidewallsurfaces defining an angle with respect to the surface of the substrateand facing towards the surface of the substrate, and a top surface thatis parallel to the surface of the substrate. The third semiconductorlayer may be formed on upper sidewall surfaces of the secondsemiconductor layer. A cross-section of the fifth semiconductor layertaken along the second direction may have a shape including a pluralityof second shapes that are connected to each other in the seconddirection. The second shapes may be on respective ones of the secondactive fins and may include upper sidewall surfaces defining an anglewith respect to the surface of the substrate and facing away from thesubstrate and lower sidewall surfaces defining an angle with respect tothe surface of the substrate and facing towards the surface of thesubstrate. The sixth semiconductor layer may be formed on the uppersidewall surfaces of the fifth semiconductor layer.

In some embodiments, a top surface of the sixth semiconductor layer maybe substantially coplanar with a top surface of the fifth semiconductorlayer.

In some embodiments, a cross-section of the sixth semiconductor layertaken along the second direction may include a top surface that issubstantially flat and substantially parallel to the surface of thesubstrate along the second direction.

In some embodiments, in a cross-section taken along the seconddirection, a thickness of the sixth semiconductor layer on outer ones ofthe upper sidewall surfaces of outermost ones of the second shapes ofthe fifth semiconductor layer may be less than a thickness of the sixthsemiconductor layer on inner ones of the upper sidewall surfaces of theoutermost ones of the second shapes of the fifth semiconductor layer andless than thicknesses of the sixth semiconductor layer on upper sidewallsurfaces of inner ones of the second shapes of the fifth semiconductorlayer.

In some embodiments, in a cross-section taken along the seconddirection, a thickness of the third semiconductor layer on uppersidewall surfaces of the second semiconductor layer may be less than athickness of the sixth semiconductor layer on inner ones of the uppersidewall surfaces of outermost ones of the second shapes of the fifthsemiconductor layer and less than thicknesses of the sixth semiconductorlayer on upper sidewall surfaces of inner ones of the second shapes ofthe fifth semiconductor layer.

In some embodiments, the first source/drain layer structure may includea first silicon layer at least partially covering the second and thirdsemiconductor layers, and the second source/drain layer structure mayinclude a second silicon layer at least partially covering the fifth andsixth semiconductor layers.

In some embodiments, a first length of the first contact plug in avertical direction that is substantially perpendicular to the surface ofthe substrate may be substantially equal to a second length of thesecond contact plug in the vertical direction.

In some embodiments, a bottom of the first contact plug may besubstantially flat and substantially parallel to the surface of thesubstrate.

In some embodiments, the semiconductor device may further include afirst metal silicide pattern between the first source/drain layerstructure and the first contact plug, and a second metal silicidepattern between the second source/drain layer structure and the secondcontact plug.

According to some embodiments of the inventive concepts, semiconductordevices are provided. A semiconductor device may include a first activefin, a plurality of second active fins, a plurality of third activefins, first, second and third gate structures, a first epitaxial layerstructure, a second epitaxial layer structure, a third epitaxial layerstructure, a first contact plug, a second contact plug, and a thirdcontact plug. The first active fin may be on a first region of a surfaceof a substrate, and the surface of the substrate may include the firstregion, a second region and a third region. The second active fins andthe third active fins may be formed on the second and third regions,respectively, of the substrate. The first, second and third gatestructures may be formed on the first, second and third active fins,respectively. The first epitaxial layer structure may be formed on thefirst active fin adjacent the first gate structure. The second epitaxiallayer structure may commonly contact upper surfaces of the second activefins adjacent the second gate structure. The third epitaxial layerstructure may commonly contact upper surfaces of the third active finsadjacent the third gate structure. The first contact plug may be formedon the first epitaxial layer structure. The second contact plug may beformed on the second epitaxial layer structure. The third contact plugmay be formed on the third epitaxial layer structure. A bottom of atleast one of the second and third contact plugs may be substantiallyflat and substantially parallel to the surface of the substrate.

In some embodiments, the second epitaxial layer structure may includesilicon-germanium, and the third epitaxial layer structure may includesilicon carbide.

In some embodiments, a bottom of the second contact plug and a bottom ofthe third contact plug may be substantially flat and substantiallyparallel to the surface of the substrate.

In some embodiments, a first length of the first contact plug in avertical direction that is substantially perpendicular to the surface ofthe substrate may be greater than second and third lengths of the secondand third contact plugs, respectively, in the vertical direction.

In some embodiments, top surfaces of the second and third epitaxiallayer structures may be farther from the surface of the substrate than atop surface of the first epitaxial layer is to the surface of thesubstrate.

In some embodiments, the second epitaxial layer may includesilicon-germanium, and the third epitaxial layer may include silicon.

In some embodiments, a bottom of the second contact plug may besubstantially flat and substantially parallel to the surface of thesubstrate, and a bottom of the third contact plug may be bent.

In some embodiments, first and third lengths of the respective first andthird contact plugs in a vertical direction that is substantiallyperpendicular to the surface of the substrate may be each greater than asecond length of the second contact plug in the vertical direction.

In some embodiments, top surfaces of the first and third epitaxial layerstructures may be each closer to the surface of the substrate than a topsurface of the second epitaxial layer is to the surface of thesubstrate.

In some embodiments, the first region may be an SRAM region including anSRAM device, and the second and third regions may be logic regionsincluding logic devices.

According to some embodiments of the inventive concepts, methods ofmanufacturing semiconductor devices are provided. In a method, anisolation pattern may be formed on a surface of a substrate. Theisolation pattern may cover lower portions of a first active fin and aplurality of second active fins. The substrate may include first andsecond regions, and the first and second active fins may be in the firstand second active regions, respectively. First and second dummy gatestructures may be formed on the first and second active fins,respectively. First and second source/drain layer structures may beformed by a selective epitaxial growth (SEG) process on portions of thefirst and second active fins that are adjacent the first and second gatestructures, respectively. The second source/drain layer structure maycommonly contact upper surfaces of the second active fins, and a topsurface of the second source/drain layer structure may be farther fromthe surface of the substrate than a top surface of the firstsource/drain layer structure is to the surface of the substrate. Thefirst and second dummy gate structures may be replaced with first andsecond gate structures, respectively.

In some embodiments, forming the first and second source/drain layerstructures may include forming first and second recesses by etchingupper portions of the first and second active fins that are adjacent thefirst and second dummy gate structures, respectively. Forming the firstand second source/drain layer structures may include forming the firstand second source/drain layer structures to fill the first and secondrecesses, respectively.

In some embodiments, the SEG process may include using a silicon sourcegas, a germanium source gas and hydrogen chloride (HCl) gas.

In some embodiments, the silicon source gas may include silane (SiH₄)gas and/or disilane (Si₂H₆) gas.

In some embodiments, the SEG process that forms the first and secondsource/drain layer structures may include a first SEG process includingproviding the silicon source gas and the germanium source gas withrespective first and second flow rates to form first and fourthsemiconductor layers in the respective first and second recesses. TheSEG process that forms the first and second source/drain layerstructures may include a second SEG process including providing thesilicon source gas and the germanium source gas with respective thirdand fourth flow rates to form second and fifth semiconductor layers onthe respective first and fourth semiconductor layers. The SEG processthat forms the first and second source/drain layer structures mayinclude a third SEG process including providing the silicon source gasand the germanium source gas with respective fifth and sixth flow ratesto form third and sixth semiconductor layers in the respective secondand fifth semiconductor layers.

In some embodiments, a ratio of the fourth flow rate to the third flowrate in the second SEG process may be greater than a ratio of the secondflow rate to the first flow rate in the first SEG process, and a ratioof the sixth flow rate to the fifth flow rate in the third SEG processmay be greater than the ratio of the fourth flow rate to the third flowrate in the second SEG process.

In some embodiments, the first to third SEG processes may furtherinclude providing p-type impurity source gases with seventh to ninthflow rates in the respective first to third SEG processes.

In some embodiments, the eighth flow rate may be greater than theseventh flow rate, and the ninth flow rate may be greater than theeighth flow rate.

In some embodiments, the second SEG process may form the second andfifth semiconductor layers having a {111} crystal plane. The third SEGprocess may form the third and sixth semiconductor layers on uppersidewall surfaces of the respective second and fifth semiconductorlayers facing away from the substrate, and not on lower sidewallsurfaces of the respective second and fifth semiconductor layers facingtowards the substrate.

In some embodiments, a cross-section of the second semiconductor layertaken along a direction that is substantially parallel to the surface ofthe substrate and parallel to the first and second gate structures mayhave a first shape that includes upper sidewall surfaces defining anangle with respect to the surface of the substrate and facing away fromthe substrate and lower sidewall surfaces defining an angle with respectto the surface of the substrate and facing towards the surface of thesubstrate. The third semiconductor layer may be formed on the uppersidewall surfaces of the second semiconductor layer. A cross-section ofthe fifth semiconductor layer taken along the direction may have a shapeincluding a plurality of second shapes that are connected to each otherin the direction. The second shapes may be on respective ones of thesecond active fins and may include upper sidewall surfaces defining anangle with respect to the surface of the substrate and facing away fromthe substrate, lower sidewall surfaces defining an angle with respect tothe surface of the substrate and facing towards the surface of thesubstrate, and a top surface that is parallel to the surface of thesubstrate. The sixth semiconductor layer may be formed on the uppersidewall surfaces of the fifth semiconductor layer.

In some embodiments, a top surface of the sixth semiconductor layer maybe substantially flat and substantially parallel to the surface of thesubstrate.

In some embodiments, a thickness of the sixth semiconductor layer onouter ones of the upper sidewall surfaces of outermost ones of thesecond shapes of the fifth semiconductor layer may be less than athickness of the sixth semiconductor layer on inner ones of the uppersidewall surfaces of the outermost ones of the second shapes of thefifth semiconductor layer and less than thicknesses of the sixthsemiconductor layer on upper sidewall surfaces of inner ones of thesecond shapes of the fifth semiconductor layer.

In some embodiments, a thickness of the third semiconductor layer onupper sidewall surfaces of the second semiconductor layer may be lessthan a thickness of the sixth semiconductor layer on inner ones of theupper sidewall surfaces of outermost ones of the second shapes of thefifth semiconductor layer and less than thicknesses of the sixthsemiconductor layer on upper sidewall surfaces of inner ones of thesecond shapes of the fifth semiconductor layer.

In some embodiments, after the third SEG process, a fourth SEG processmay include providing dichlorosilane (SiH₂Cl₂) gas to form first andsecond silicon layers on the third and sixth semiconductor layers,respectively.

In some embodiments, the SEG process may include using a silicon sourcegas, a carbon source gas and hydrogen chloride (HCl) gas.

In some embodiments, the silicon source gas may include silane (SiH₄)gas and/or disilane (Si₂H₆) gas.

In some embodiments, the SEG process that forms the first and secondsource/drain layer structures may include a first SEG process includingproviding the silicon source gas and the carbon source gas withrespective first and second flow rates to form first and fourthsemiconductor layers in the respective first and second recesses. TheSEG process that forms the first and second source/drain layerstructures may include a second SEG process including providing thesilicon source gas and the carbon source gas with respective third andfourth flow rates to form second and fifth semiconductor layers on therespective first and fourth semiconductor layers. The SEG process thatforms the first and second source/drain layer structures may include athird SEG process including providing the silicon source gas and thecarbon source gas with respective fifth and sixth flow rates to formthird and sixth semiconductor layers in the respective second and fifthsemiconductor layers.

In some embodiments, the first to third SEG processes may furtherinclude providing n-type impurity source gases with seventh to ninthflow rates in the respective first to third SEG processes.

In some embodiments, the second SEG process may form the second andfifth semiconductor layers having a {111} crystal plane. The third SEGprocess may form the third and sixth semiconductor layers on uppersidewall surfaces of the respective second and fifth semiconductorlayers facing away from the substrate, and not on lower sidewallsurfaces of the respective second and fifth semiconductor layers facingtowards the substrate.

In some embodiments, after the first and second source/drain layerstructures are formed, an insulating interlayer covering the first andsecond source/drain layer structures and sidewalls of the first andsecond dummy gate structures may be formed. After the first and seconddummy gate structures are replaced with the first and second gatestructures, the insulating interlayer may be partially etched to formfirst and second contact holes that expose upper surfaces of the firstand second source/drain layer structures. First and second contact plugsmay be formed in the first and second contact holes, respectively.

In some embodiments, the first contact hole may be deeper than thesecond contact hole.

In some embodiments, bottoms of the first and second contact holes maybe flat.

In some embodiments, bottoms of the first and second contact holes maybe bent.

In some embodiments, after the first and second contact holes areformed, first and second metal silicide patterns may be formed on thefirst and second source/drain layer structures exposed by the first andsecond contact holes, respectively.

According to some embodiments of the inventive concepts, methods ofmanufacturing semiconductor devices are provided. In a method, anisolation pattern may be formed on a surface of a substrate. Theisolation pattern may cover lower portions of a first active fin and aplurality of second active fins. The substrate may include first andsecond regions, and the first and second active fins may be in the firstand second active regions, respectively. First and second dummy gatestructures may be formed on the first and second active fins,respectively. First and second source/drain layer structures may beformed by an SEG process on portions of the first and second active finsthat are adjacent the first and second gate structures, respectively.The second source/drain layer structure may commonly contact uppersurfaces of the second active fins, and a top surface of the secondsource/drain layer structure may be substantially coplanar with a topsurface of the first source/drain layer structure. The first and seconddummy gate structures may be replaced with first and second gatestructures, respectively. A first contact plug may be formed on thefirst source/drain layer structure. A second contact plug may be formedon the second source/drain layer structure, and a bottom of the secondcontact plug may be substantially flat and substantially parallel to thesurface of the substrate.

In some embodiments, forming the first and second source/drain layerstructures may include forming first and second recesses by etchingupper portions of the first and second active fins that are adjacent thefirst and second dummy gate structures, respectively. The SEG processmay include using a silicon source gas, a germanium source gas andhydrogen chloride (HCl) gas to form the first and second source/drainlayer structures filling the first and second recesses, respectively.The silicon source gas may include silane (SiH₄) gas and/or disilane(Si₂H₆) gas.

In some embodiments, the SEG process that forms the first and secondsource/drain layer structures may include a first SEG process includingproviding the silicon source gas and the germanium source gas withrespective first and second flow rates to form first and fourthsemiconductor layers in the respective first and second recesses. TheSEG process that forms the first and second source/drain layerstructures may include a second SEG process including providing thesilicon source gas and the germanium source gas with respective thirdand fourth flow rates to form second and fifth semiconductor layers onthe respective first and fourth semiconductor layers. The SEG processthat forms the first and second source/drain layer structures mayinclude a third SEG process including providing the silicon source gasand the germanium source gas with respective fifth and sixth flow ratesto form third and sixth semiconductor layers in the respective secondand fifth semiconductor layers.

In some embodiments, the second SEG process may form the second andfifth semiconductor layers having a {111} crystal plane. The third SEGprocess may form the third and sixth semiconductor layers on uppersidewall surfaces of the respective second and fifth semiconductorlayers facing away from the substrate and not on lower sidewall surfacesof the respective second and fifth semiconductor layers facing towardsthe substrate in the third SEG process.

In some embodiments, a cross-section of the second semiconductor layertaken along a direction that is substantially parallel to the surface ofthe substrate and parallel to the first and second gate structures mayhave a first shape comprising upper sidewall surfaces defining an anglewith respect to the surface of the substrate and facing away from thesubstrate and lower sidewall surfaces defining an angle with respect tothe surface of the substrate and facing towards the surface of thesubstrate. The third semiconductor layer may be formed on the uppersidewall surfaces of the second semiconductor layer. A cross-section ofthe fifth semiconductor layer taken along the direction may have a shapeincluding a plurality of second shapes that are connected to each otherin the direction. The second shapes may be on respective ones of thesecond active fins and may include upper sidewall surfaces defining anangle with respect to the surface of the substrate and facing away fromthe substrate, lower sidewall surfaces defining an angle with respect tothe surface of the substrate and facing towards the surface of thesubstrate, and a top surface that is parallel to the surface of thesubstrate. The sixth semiconductor layer may be formed on upper sidewallsurfaces of the fifth semiconductor layer.

In some embodiments, a top surface of the sixth semiconductor layer maybe substantially flat and substantially parallel to the surface of thesubstrate.

According to some embodiments of the inventive concepts, methods ofmanufacturing semiconductor devices are provided. In a method, anisolation pattern may be formed on a surface of a substrate. Theisolation pattern may cover lower potions of a first active fin, aplurality of second active fins, and a plurality of third active fins.The substrate may include first, second and third regions, and the firstto third active fins may be in the first to third active regions,respectively. First, second and third dummy gate structures may beformed on the first to third active fins, respectively. First, secondand third source/drain layer structures may be formed in an SEG processon portions of the first to third active fins that are adjacent thefirst to third gate structures, respectively. The second source/drainlayer structure may commonly contact upper surfaces of the second activefins, and the third source/drain layer structure may commonly contactupper surfaces of the third active fins. The first to third dummy gatestructures may be replaced with first, second and third gate structures,respectively. First, second and third contact plugs may be formed on thefirst to third source/drain layer structures, respectively. A bottom ofat least one of the second and third contact plugs may be substantiallyflat and substantially parallel to the surface of the substrate.

In some embodiments, the first source/drain layer structures onneighboring ones of the first active fins may not be electricallyconnected to each other, while the second source/drain layer commonlycontacting neighboring ones of the second active fins may have a desiredvolume. Thus, the electrical failure between the first transistors maybe prevented in the first region, while a proper stress may be appliedto the channel of the second transistor and the performance of thesecond transistor may be improved.

According to some embodiments of the inventive concepts, semiconductordevices are provided. A semiconductor device may include a substrate.The semiconductor device may include an active fin on the substrate thatmay extend with a longest dimension in a first direction that isparallel to a surface of the substrate. The semiconductor device mayinclude a gate pattern on the active fin that may extend with a longestdimension in a second direction that is parallel to the surface of thesubstrate and that crosses the first direction. The semiconductor devicemay include a first semiconductor layer that may be on a bottom andsidewalls of a recessed portion of the active fin that is adjacent thegate pattern. The first semiconductor layer may include silicongermanium with a first germanium concentration. The semiconductor devicemay include a second semiconductor layer on the first semiconductorlayer having a cross-section taken in the second direction comprisingupper sidewall surfaces defining an angle with respect to the surface ofthe substrate and facing away from the substrate and lower sidewallsurfaces defining an angle with respect to the surface of the substrateand facing towards the surface of the substrate. The secondsemiconductor layer may include silicon germanium with a secondgermanium concentration that is greater than the first germaniumconcentration. The semiconductor device may include a thirdsemiconductor layer that is on the upper sidewall surfaces of the secondsemiconductor layer and not on the lower sidewall surfaces of the secondsemiconductor layer. The third semiconductor layer may include silicongermanium with a third germanium concentration that is greater than thesecond germanium concentration.

In some embodiments, the first semiconductor layer may include p-typeimpurities with a first impurity concentration. The second semiconductorlayer may include p-type impurities with a second impurity concentrationthat is greater than the first impurity concentration. The thirdsemiconductor layer may include p-type impurities with a third impurityconcentration that is greater than the second impurity concentration.

In some embodiments, the active fin and the gate pattern may be a firstactive fin and a first gate pattern, respectively, on a first region ofthe substrate. The semiconductor device may further include a pluralityof second active fins on a second region of the substrate that extendparallel to each other with longest dimensions in the first direction.The semiconductor device may include a second gate pattern on theplurality of second active fins that extends with a longest dimension inthe second direction. The semiconductor device may include a pluralityof fourth semiconductor layers that are on bottoms and sidewalls ofrecessed portions of respective ones of the plurality of second activefins that are adjacent the second gate pattern. The fourth semiconductorlayers may include silicon germanium with a fourth germaniumconcentration and being spaced apart from each other. The semiconductordevice may include a fifth semiconductor layer on the plurality offourth semiconductor layers. The fifth semiconductor layer may include aplurality of shapes. Ones of the plurality of shapes may be onrespective ones of the plurality of fourth semiconductor layers and mayhave a cross-section taken in the second direction comprising uppersidewall surfaces defining an angle with respect to the surface of thesubstrate and facing away from the substrate and lower sidewall surfacesdefining an angle with respect to the surface of the substrate andfacing towards the surface of the substrate. The fifth semiconductorlayer may include silicon germanium with a fifth germanium concentrationthat is greater than the fourth germanium concentration. Adjacent onesof the shapes of the fifth semiconductor layer may contact each other.The semiconductor device may include a sixth semiconductor layer that ison the upper sidewall surfaces of the shapes of the fifth semiconductorlayer and not on the lower sidewall surfaces of the shapes of the fifthsemiconductor layer. The sixth semiconductor layer may include silicongermanium with a sixth germanium concentration that is greater than thefifth germanium concentration.

In some embodiments, the plurality of second active fins may include twooutermost ones of the second active fins and at least one inner secondactive fin that is between the outermost ones of the second active fins.The plurality of shapes of the fifth semiconductor layer may includeoutermost shapes on the outermost ones of the second active fins and atleast one inner shape that is on the at least one inner second activefin. The outermost shapes of the fifth semiconductor layer may includeinner upper sidewall surfaces that are adjacent to the at least oneinner shape and outer upper sidewall surfaces opposite from the at leastone inner shape.

A thickness of the third semiconductor layer on the upper sidewallsurfaces of the second semiconductor layer may be less than a thicknessof the sixth semiconductor layer on the inner upper sidewall surfaces ofthe outermost shapes of the fifth semiconductor layer and less thanthicknesses of the sixth semiconductor layer on the upper sidewallsurfaces of the inner shapes of the fifth semiconductor layer. Athickness of the sixth semiconductor layer on the outer upper sidewallsurfaces of the outermost shapes of the fifth semiconductor layer may beless than a thickness of the sixth semiconductor layer on the innerupper sidewall surfaces of the outermost shapes of the fifthsemiconductor layer and less than thicknesses of the sixth semiconductorlayer on the upper sidewall surfaces of the inner shapes of the fifthsemiconductor layer.

In some embodiments, the semiconductor device may further include aplurality of third active fins on a third region of the substrate thatextend parallel to each other with longest dimensions in the firstdirection. The plurality of third active fins may include outermost onesof the third active fins and at least one inner third active fin that isbetween the outermost ones of the third active fins. The semiconductordevice may include a third gate pattern on the plurality of third activefins that extends with a longest dimension in the second direction. Thesemiconductor device may include a plurality of seventh semiconductorlayers that are on bottoms and sidewalls of recessed portions ofrespective ones of the plurality of second active fins that are adjacentthe second gate pattern. The seventh semiconductor layers may includesilicon carbide with a first carbon concentration and may be spacedapart from each other. The semiconductor device may include an eighthsemiconductor layer on the plurality of seventh semiconductor layers.The eighth semiconductor layer may include a plurality of shapes. Onesof the plurality of shapes may be on respective ones of the plurality ofseventh semiconductor layers and may have a cross-section taken in thesecond direction comprising upper sidewall surfaces defining an anglewith respect to the surface of the substrate and facing away from thesubstrate and lower sidewall surfaces defining an angle with respect tothe surface of the substrate and facing towards the surface of thesubstrate. The eighth semiconductor layer may include silicon carbidewith a second carbon concentration that is greater than the first carbonconcentration. Adjacent ones of the shapes of the eighth semiconductorlayer may contact each other. The semiconductor device may include aninth semiconductor layer that is on the upper sidewall surfaces of theshapes of the eighth semiconductor layer and not on the lower sidewallsurfaces of the shapes of the eighth semiconductor layer. The ninthsemiconductor layer may include silicon carbide with a third carbonconcentration that is greater than the second carbon concentration.

It is noted that aspects of the inventive concepts described withrespect to one embodiment may be incorporated in a different embodimentalthough not specifically described relative thereto. That is, allembodiments and/or features of any embodiment can be combined in any wayand/or combination. These and other objects and/or aspects of thepresent inventive concepts are explained in detail in the specificationset forth below.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features, and advantages of the presentdisclosure will become more apparent to those of ordinary skill in theart by describing in detail embodiments of the inventive conceptsthereof with reference to the accompanying drawings, in which:

FIGS. 1 to 59 are plan views and cross-sectional views schematicallyillustrating intermediate process operations of methods of manufacturingsemiconductor devices according to some embodiments of the inventiveconcepts; and

FIGS. 60 to 100 are plan views and cross-sectional views schematicallyillustrating intermediate process operations of methods of manufacturingsemiconductor devices according to some embodiments of the inventiveconcepts.

DETAILED DESCRIPTION OF EMBODIMENTS

The inventive concepts will be described more fully hereinafter withreference to the accompanying drawings, in which some embodiments areshown. The present inventive concepts may, however, be embodied in manydifferent forms and should not be construed as limited to theembodiments set forth herein. In the drawings, the sizes and relativesizes of layers and regions may be exaggerated for clarity.

It will be understood that when an element or layer is referred to asbeing “on,” “connected to” or “coupled to” another element or layer, itmay be directly on, connected or coupled to the other element or layeror intervening elements or layers may be present. In contrast, when anelement is referred to as being “directly on,” “directly connected to”or “directly coupled to” another element or layer, there are nointervening elements or layers present. Like reference numerals refer tolike elements throughout. As used herein, the term “and/or” includes anyand all combinations of one or more of the associated listed items.

It will be understood that, although the terms first, second, third,fourth etc. may be used herein to describe various elements, components,regions, layers and/or sections, these elements, components, regions,layers and/or sections should not be limited by these terms. These termsmay be used to distinguish one element, component, region, layer orsection from another region, layer or section. Thus, a first element,component, region, layer or section discussed below could be termed asecond element, component, region, layer or section without departingfrom the teachings of the present inventive concepts.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,”“upper” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the exemplary term “below” can encompass both anorientation of above and below. The device may be otherwise oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly. As used herein, unlessotherwise described, a surface or other element referred to as “top” or“upper” is a surface or element that is more remote from a substrate ina direction that is perpendicular to a major surface of the substrate ascompared to other surfaces or elements. As used herein, unless otherwisedescribed, a surface or other element referred to as “bottom” or “lower”is closer to a substrate in a direction that is perpendicular to a majorsurface of the substrate as compared to other surfaces or elements.

The terminology used herein is for the purpose of describing someembodiments of the inventive concepts and is not intended to be limitingof the present inventive concepts. As used herein, the singular forms“a,” “an” and “the” are intended to include the plural forms as well,unless the context clearly indicates otherwise. It will be furtherunderstood that the terms “comprises” and/or “comprising,” when used inthis specification, specify the presence of stated features, integers,steps, operations, elements, and/or components, but do not preclude thepresence or addition of one or more other features, integers, steps,operations, elements, components, and/or groups thereof.

Embodiments may be described herein with reference to cross-sectionalillustrations that are schematic illustrations of idealized exampleembodiments (and intermediate structures). As such, variations from theshapes of the illustrations as a result, for example, of manufacturingtechniques and/or tolerances, are to be expected. Thus, embodimentsshould not be construed as limited to the particular shapes of regionsthat are illustrated herein but are to include deviations in shapes thatresult, for example, from manufacturing. For example, an implantedregion that is illustrated as a rectangle may, typically, have roundedor curved features and/or a gradient of implant concentration at itsedges rather than a binary change from implanted to non-implantedregion. Likewise, a buried region formed by implantation may result insome implantation in the region between the buried region and thesurface through which the implantation takes place. Thus, the regionsthat are illustrated in the figures are schematic in nature and theirshapes are not intended to illustrate the actual shape of a region of adevice and are not intended to limit the scope of the present inventiveconcepts.

Elements may be illustrated and/or described in singular and/or pluralform. However, it will be understood that, unless otherwise describedherein, embodiments may contain multiple instances of like elements.Descriptions in singular form may apply to one or more of a plurality ofelements present in embodiments of the inventive concept.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this inventive concepts belong. Itwill be further understood that terms, such as those defined in commonlyused dictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

FIGS. 1 to 59 are plan views and cross-sectional views schematicallyillustrating intermediate operations of methods of manufacturingsemiconductor devices according to some embodiments of the inventiveconcepts. Particularly, FIGS. 1, 4, 6, 9, 12, 17, 21, 28, 32, 36 and 43are plan views, and FIGS. 2-3, 5, 7-8, 10-11, 13-16, 18-20, 22-27,29-31, 33-35, 37-42 and 44-59 are cross-sectional views.

FIGS. 2-3, 5, 10, 13, 15-16, 18, 22, 25, 27, 29, 37, 40, 44, 48, 51, 54,57 and 59 are cross-sectional views taken along lines A-A′ ofcorresponding plan views, respectively. FIGS. 7, 33 and 45 arecross-sectional views taken along lines B-B′ of corresponding planviews, respectively. FIGS. 8, 11, 14, 19, 23, 30, 34, 38, 41, 46, 49, 52and 55 are cross-sectional views taken along lines C-C′ of correspondingplan views, respectively. FIGS. 20, 24, 26, 31, 35, 39, 42, 47, 50, 53,56 and 58 are cross-sectional views taken along lines D-D′ ofcorresponding plan views, respectively.

Referring to FIGS. 1 and 2 , an upper portion of a substrate 100 may bepartially etched to form first and second recesses 112 and 114. Thesubstrate 100 may include a semiconductor material, e.g., silicon,germanium, silicon-germanium, etc., or III-V semiconductor compounds,e.g., GaP, GaAs, GaSb, etc. In some embodiments, the substrate 100 maybe a silicon-on-insulator (SOI) substrate, or a germanium-on-insulator(GOI) substrate.

The substrate 100 may include first and second regions I and II. In someembodiments, the first region I may serve as a static random accessmemory (SRAM) region in which SRAM devices may be formed, and the secondregion II may serve as a logic region in which logic devices may beformed. Alternatively, both of the first and second regions I and II mayserve as logic regions or peripheral circuit regions in which peripheralcircuits for memory devices may be formed. A width of the first recess112 in the first region I may be greater than a width of the secondrecess 114 in the second region II.

As the first and second recesses 112 and 114 are formed on the substrate100, first and second active regions 102 and 104 may be defined in thefirst and second regions I and II, respectively, of the substrate 100.The first and second active regions 102 and 104 may protrude from anupper surface of the substrate 100, and thus may be also referred to asfirst and second active fins 102 and 104. A region of the substrate 100in which the first and second active fins 102 and 104 are not formed maybe referred to as a field region.

In some embodiments, the first and second active fins 102 and 104 mayextend in a first direction that is substantially parallel to the uppersurface of the substrate 100, and a plurality of first active fins 102and a plurality of second active fins 104 may be formed in a seconddirection, which may be substantially parallel to the upper surface ofthe substrate 100 and may cross the first direction. For example, thefirst and second directions may cross each other at a right angle, andthus may be substantially perpendicular to each other. In other wordsthe first and second active fins 102 and 104 may extend perpendicular toeach other with a longest dimension of ones of the first and secondactive fins 102 and 104 in the first direction and separated from eachother by distances between each other in the second direction. In someembodiments, a distance between the first active fins 102 in the seconddirection may be greater than a distance between the second active fins104 in the second direction.

In some embodiments, ones of the first and second active fins 102 and104 may have a constant width from a top toward a bottom thereof, or asidewall of ones of the first and second active fins 102 and 104 mayhave a constant slope with respect to the upper surface of the substrate100.

However, referring to FIG. 3 , in some embodiments, ones of the firstand second active fins 102 and 104 may have a width gradually increasingfrom a top toward a bottom thereof and a slope of the sidewall maygradually decrease. Hereinafter, for the convenience of explanation,only the first and second active fins 102 and 104 as shown in FIG. 2will be described.

Referring to FIGS. 4 and 5 , an isolation pattern 120 may be formed onthe substrate 100 to fill lower portions of the first and secondrecesses 112 and 114. In some embodiments, the isolation pattern 120 maybe formed by forming an isolation layer on the substrate 100 tosufficiently fill the first and second recesses 112 and 114, planarizingthe isolation layer until upper surfaces of the first and second activefins 102 and 104 may be exposed, and removing an upper portion of theisolation layer to expose upper portions of the first and secondrecesses 112 and 114. The isolation pattern 120 may be a portion of theisolation layer remaining after removing the upper portion of theisolation layer. In some embodiments, the isolation layer may be formedof an oxide, e.g., silicon oxide.

In some embodiments, ones of the first active fins 102 may include afirst lower active pattern 102 b whose sidewall may be covered by theisolation pattern 120, and a first upper active pattern 102 a that isnot covered by the isolation pattern 120 but protruding therefrom.Additionally, ones of the second active fins 104 may include a secondlower active pattern 104 b whose sidewall may be covered by theisolation pattern 120, and a second upper active pattern 104 a that isnot covered by the isolation pattern 120 but protruding therefrom. Insome embodiments, the first and second upper active patterns 102 a and104 a may have widths in the second direction that may be slightly lessthan widths of the first and second lower active patterns 102 b and 104b, respectively.

In some embodiments, the isolation pattern 120 may be formed to have amulti-layered structure. Particularly, the isolation pattern 120 mayinclude first and second liners sequentially stacked on an inner wall ofones of the first and second recesses 112 and 114, and a fillinginsulation layer filling a remaining portion of the first and secondrecesses 112 and 114 on the second liner. For example, the first linermay be formed of an oxide, e.g., silicon oxide, the second liner may beformed of a nitride, e.g., silicon nitride, or polysilicon, and thefilling insulation layer may be formed of an oxide, e.g., silicon oxide.

Referring to FIGS. 6 to 8 , first and second dummy gate structures maybe formed on the first and second regions I and II, respectively, of thesubstrate 100.

The first and second dummy gate structures may be formed by sequentiallyforming a dummy gate insulation layer, a dummy gate electrode layer anda dummy gate mask layer on the first and second active fins 102 and 104of the substrate 100 and the isolation pattern 120, patterning the dummygate mask layer to form first and second dummy gate masks 152 and 154 inthe first and second regions I and II, respectively, and sequentiallyetching the dummy gate electrode layer and the dummy gate insulationlayer using the first and second dummy gate masks 152 and 154 as anetching mask.

Thus, the first dummy gate structure may include a first dummy gateinsulation pattern 132, a first dummy gate electrode 142 and the firstdummy gate mask 152 sequentially stacked on the first region I of thesubstrate 100, and the second dummy gate structure may include a seconddummy gate insulation pattern 134, a second dummy gate electrode 144 andthe second dummy gate mask 154 sequentially stacked on the second regionII of the substrate 100

In some embodiments, the dummy gate insulation layer may be formed of anoxide, e.g., silicon oxide, the dummy gate electrode layer may be formedof, e.g., polysilicon, and the dummy gate mask layer may be formed of anitride, e.g., silicon nitride. In some embodiments, the dummy gateinsulation layer may be formed by a chemical vapor deposition (CVD)process, an atomic layer deposition (ALD) process, etc. Alternatively,the dummy gate insulation layer may be formed by a thermal oxidationprocess on an upper portion of the substrate 100, and in this case, thedummy gate insulation layer may be formed only on the first and secondupper active patterns 102 a and 104 a. The dummy gate electrode layerand the dummy gate mask layer may be formed by a CVD process, an ALDprocess, etc.

In some embodiments, the first and second dummy gate structures may beformed to extend in the second direction, and a plurality of first dummygate structures and a plurality of second dummy gate structures may beformed in the first direction. FIGS. 6 to 8 show that the first andsecond dummy gate structures extend in the second direction along thesame line, however, the inventive concepts may not be limited thereto,and the first and second dummy gate structures may extend alongdifferent lines. In other words, first and second dummy gate structuresmay be offset from each other.

Referring to FIGS. 9 to 11 , first and second gate spacers 162 and 164may be formed on sidewalls of the first and second dummy gatestructures, respectively. First and second fin spacers 172 and 174 maybe also formed on sidewalls of the first and second upper activepatterns 102 a and 104 a, respectively. In some embodiments, the firstand second gate spacers 162 and 164 and the first and second fin spacers172 and 174 may be formed by forming a spacer layer on the first andsecond dummy gate structures, the first and second active fins 102 and104 and the isolation pattern 120, and anisotropically etching thespacer layer. The spacer layer may be formed of a nitride, e.g., siliconnitride, silicon oxycarbonitride, etc.

The first and second gate spacers 162 and 164 may be formed on oppositesidewalls of the first and second dummy gate structures, respectively,in the first direction, and the first and second fin spacers 172 and 174may be formed on opposite sidewalls of the first and second active fins102 and 104, respectively, in the second direction.

Referring to FIGS. 12 to 14 , upper portions of the first and secondactive fins 102 and 104 that are adjacent the first and second dummygate structures, respectively, may be etched to form third and fourthrecesses 182 and 184, respectively.

Particularly, the upper portions of the first and second active fins 102and 104 may be removed using the first and second dummy gate structuresand the first and second gate spacers 162 and 164 on sidewalls thereofas an etching mask to form the third and fourth recesses 182 and 184.The first and second fin spacers 172 and 174 may be also removed.

FIGS. 12 to 14 show that the first and second upper active patterns 102a and 104 a of the first and second active fins 102 and 104,respectively, may be partially removed to form the third and fourthrecesses 182 and 184, respectively, however, the inventive concepts maynot be limited thereto. In some embodiments, not only the first andsecond upper active patterns 102 a and 104 a but also portions of thefirst and second lower active patterns 102 b and 104 b may be removed toform the third and fourth recesses 182 and 184. In some embodiments, theetching process for forming the first and second gate spacers 162 and164 and the etching process for forming the third and fourth recesses182 and 184 may be performed in-situ. In some embodiments, the third andfourth recesses 182 and 184 may be formed to have substantially the samedepth, and thus top surfaces of the remaining first and second activefins 102 and 104 under the third and fourth recesses 182 and 184,respectively, may have substantially the same height.

Alternatively, referring to FIG. 15 , the third and fourth recesses 182and 184 may be formed to have different depths from each other, and thusthe top surfaces of the remaining first and second active fins 102 and104 under the third and fourth recesses 182 and 184, respectively, mayhave different heights from each other. In some embodiments, the topsurface of the first active fin 102 may be higher than that of thesecond active fin 104. Hereinafter, for the convenience of explanation,only the first and second active fins 102 and 104 as shown in FIGS. 12to 14 will be described.

Referring to FIG. 16 , when the upper portions of the first and secondactive fins 102 and 104 are etched to form the third and fourth recesses182 and 184, respectively, an upper portion of the isolation pattern 120may be partially etched to form a fifth recess 125 thereon. In someembodiments, the fifth recess 125 may have a central bottom lower thanedge bottoms adjacent the first and second active fins 102 and 104.

Referring to FIGS. 17 to 20 , first and fourth semiconductor layers 202a and 204 a may be formed in the third and fourth recesses 182 and 184,respectively, and second and fifth semiconductor layers 202 b and 204 bmay be formed on the first and fourth semiconductor layers 202 a and 204a, respectively. In some embodiments, the first and fourth semiconductorlayers 202 a and 204 a may be formed by a first selective epitaxialgrowth (SEG) process using upper surfaces of the first and second activefins 102 and 104 exposed by the third and fourth recesses 182 and 184,respectively, as a seed. Thus, the first and fourth semiconductor layers202 a and 204 a may be conformally formed on bottoms and oppositesidewalls of the third and fourth recesses 182 and 184, respectively, inthe first direction.

In some embodiments, the first SEG process may be formed by loading thesubstrate 100 having the resultant structures thereon into a processchamber, and providing a silicon source gas, a germanium source gas, anetching gas and a carrier gas. The first SEG process may be performedusing e.g., silane (SiH₄) gas, disilane (Si₂H₆) gas, dichlorosilane(DCS) (SiH₂Cl₂) gas, etc., serving as the silicon source gas, e.g.,germane (GeH₄) gas serving as the germanium source gas, e.g., hydrogenchloride (HCl) gas serving as the etching gas, and e.g., hydrogen (H₂)gas serving as the carrier gas. Thus, a respective single crystallinesilicon-germanium layer may be formed to serve as ones of the first andfourth semiconductor layers 202 a and 204 a. In some embodiments, thesilicon source gas may be provided with a first flow rate, and thegermanium source gas may be provided with a second flow rate in thefirst SEG process.

In the first SEG process, a p-type impurity source gas, e.g., diborane(B₂H₆) gas may be also used to form a respective single crystallinesilicon-germanium layer doped with p-type impurities serving as ones ofthe first and fourth semiconductor layers 202 a and 204 a. In someembodiments, the p-type impurity source gas may be provided with a thirdflow rate in the first SEG process.

In some embodiments, the second and fifth semiconductor layers 202 b and204 b may be formed on the first and fourth semiconductor layers 202 aand 204 a, respectively, by a second SEG process. In some embodiments,the second SEG process may be performed using substantially the samegases as the first SEG process, and thus a respective single crystallinesilicon-germanium layer may be formed to serve as ones of the second andfifth semiconductor layers 202 b and 204 b. However, the flow rates ofthe gases may be controlled so that the second and fifth semiconductorlayers 202 b and 204 b may have a germanium concentration greater thanthat of the first and fourth semiconductor layers 202 a and 204 a. Insome embodiments, the silicon source gas may be provided with a fourthflow rate less than the first flow rate, and the germanium source gasmay be provided with a fifth flow rate greater than the second flow ratein the second SEG process.

Thus, when the substrate 100 is a silicon substrate, the first andfourth semiconductor layers 202 a and 204 a having a relatively lowgermanium concentration may be formed between the substrate 100 and thesecond and fifth semiconductor layers 202 b and 204 b, respectively, andthus the lattice mismatch between the second and fifth semiconductorlayers 202 b and 204 b and the first and second active fins 102 and 104,respectively, may decrease. Thus, the first and fourth semiconductorlayers 202 a and 204 a may serve as a buffer layer between the substrate100 and the second and fifth semiconductor layers 202 b and 204 b,respectively.

The flow rate of the p-type impurity source gas provided in the secondSEG process may be controlled so that the second and fifth semiconductorlayers 202 b and 204 b may have a p-type impurity concentration greaterthan that of the first and fourth semiconductor layers 202 a and 204 a.In some embodiments, the p-type impurity source gas, e.g., diborane(B₂H₆) gas may be provided with a sixth flow rate greater than the thirdflow rate in the second SEG process.

The second and fifth semiconductor layers 202 b and 204 b may be formedon the first and fourth semiconductor layers 202 a and 204 a,respectively, to partially fill the third and fourth recesses 182 and184, respectively, and may be grown in both vertical and horizontaldirections. For example, when the substrate 100 is a (111) siliconsubstrate and the first and second active fins 102 and 104 have the<110> crystal direction, the second and fifth semiconductor layers 202 band 204 b may have a growth rate lowest in the <111> crystal direction,and thus the second and fifth semiconductor layers 202 b and 204 b mayhave the {111} crystal plane.

In some embodiments, the second semiconductor layer 202 b may have across-section taken along the second direction, and the cross-section ofthe second semiconductor layer 202 b may have a first shape with fivesides similar to a pentagon. In the first shape, four of the sides, notincluding a bottom side that is adjacent to an upper surface of thesubstrate 100 or an upper surface of the isolation pattern 120, may havean angle of about 54.7 degrees with respect to the upper surface of thesubstrate 100 or the upper surface of the isolation pattern 120.

As used herein, a semiconductor layer may be described as having across-sectional shape that is similar to a pentagon when thesemiconductor layer has a cross-sectional shape that includes fivesides. However, one of the sides of the first shape that is similar to apentagon of the second semiconductor layer 202 b may be partially orcompletely consumed by the first semiconductor layer 202 a and/or thefirst upper active pattern 102 a. Therefore the first shape of thesecond semiconductor layer 202 b may be referred to as being similar toa pentagon even where the bottom side of the first shape is partially orcompletely within other structures and the perimeter of the actualcross-sectional shape of the second semiconductor layer 202 b maycontain additional sides that are adjacent to sidewalls of the firstupper active pattern 102 a, sidewalls of the first semiconductor layer202 a, and/or an upper surface of the first semiconductor layer 202 a,as illustrated in FIG. 18 .

In other words, as illustrated in FIG. 18 , the shape of the secondsemiconductor layer 202 b may include upper sidewall surfaces definingan angle with respect to the surface of the substrate and facing awayfrom the substrate and lower sidewall surfaces defining an angle withrespect to the surface of the substrate and facing towards the surfaceof the substrate.

The second semiconductor layer 202 b may also grow from portions of thefirst semiconductor layer 202 a on opposite sidewalls of the thirdrecess 182 in the first direction to have the {111} crystal plane, andthus may have a cross-section taken along the first direction whoseupper portion may have a V-like shape, as illustrated in FIG. 19 .

In some embodiments, the fifth semiconductor layer 204 b may have asecond shape similar to that of the first shape of the secondsemiconductor layer 202 b on the second active fins 104. However, across-section of the fifth semiconductor layer 204 b taken along thesecond direction may have a shape that may be formed by connecting thesecond shapes on the second active fins 104, respectively, adjacent toeach other in the second direction.

As used herein, the cross-section of the fifth semiconductor layer 204 btaken along the second direction may be referred to as being a shapethat may be formed by connecting shapes that are similar to a pentagoneven though a bottom side of the shapes that are similar to a pentagonmay be partially or completely within other structures, the actualcross-sectional shape may have additional sides adjacent to the secondupper active pattern 104 a and the fourth semiconductor layer 204 a, andone or more corners of the shapes that are similar to a pentagon may notbe present where the shapes that are similar to a pentagon connect.

In other words, as illustrated in FIG. 18 , the shape of the secondsemiconductor layer 204 b may include a shape including a plurality ofsecond shapes that are connected to each other in the second direction.The second shapes may include upper sidewall surfaces defining an anglewith respect to the surface of the substrate and facing away from thesubstrate and lower sidewall surfaces defining an angle with respect tothe surface of the substrate and facing towards the surface of thesubstrate. The second shapes may include outermost ones of the secondshapes and at least one inner second shape that is between the outermostones of the second shapes. The outermost ones of the second shapes mayhave inner upper sidewall surfaces that are adjacent to the at least oneinner second shape and outer upper sidewall surf aces that are oppositefrom the at least one inner second shape.

Referring to FIGS. 21 to 24 , a third SEG process may be performed toform third and sixth semiconductor layers 202 c and 204 c on the secondand fifth semiconductor layers 202 b and 204 b, respectively. The thirdSEG process may be performed using a silicon source gas, a germaniumsource gas, an etching gas and a carrier gas like the first and secondSEG processes. Thus, a respective single crystalline silicon-germaniumlayer may be formed as each of the third and sixth semiconductor layers202 c and 204 c.

However, the third and sixth semiconductor layers 202 c and 204 c may beformed to have a germanium concentration greater than that of the secondand fifth semiconductor layers 202 b and 204 b by controlling flow ratesof the above gases. In some embodiments, the silicon source gas may beprovided with a seventh flow rate less than the fourth flow rate, andthe germanium source gas may be provided with an eighth flow rategreater than the fifth flow rate in the third SEG process.

Additionally, the third and sixth semiconductor layers 202 c and 204 cmay be formed to have a p-type impurity concentration greater than thatof the second and fifth semiconductor layers 202 b and 204 b bycontrolling flow rates of the p-type impurity source gas. In someembodiments, the p-type impurity source gas may be provided with a ninthflow rate greater than the sixth flow rate in the third SEG process.

However, unlike the first and second SEG processes, dichlorosilane(SiH₂Cl₂) gas may not be used as the silicon source gas but silane(SiH₄) gas and/or disilane (Si₂H₆) gas may be used in the third SEGprocess. When dichlorosilane (SiH₂Cl₂) gas is provided as the siliconsource gas, it may be diffused upwardly from the first and second activefins 102 and 104 under the second and fifth semiconductor layers 202 band 204 b, respectively, and the third and sixth semiconductor layers202 c and 204 c may be also formed on lower side surfaces of the secondand fifth semiconductor layers 202 b and 204 b, respectively. However,in some embodiments, silane (SiH₄) gas and/or disilane (Si₂H₆) gas maybe provided as the silicon source gas, and it may be prevented fromdiffusing upwardly from the first and second active fins 102 and 104 sothat the third and sixth semiconductor layers 202 c and 204 c may not beformed on the lower side surfaces of the second and fifth semiconductorlayers 202 b and 204 b, respectively. This may be enhanced by properlycontrolling the flow rates of hydrogen chloride (HCl) gas serving as theetching gas and hydrogen (H₂) gas serving as the carrier gas. Therefore,in some embodiments, the third and sixth layers 202 c and 204 c may notbe formed on the lower side surfaces of the second and fifthsemiconductor layers 202 b and 204 b, respectively, but formed only onupper side surfaces of the second and fifth semiconductor layers 202 band 204 b, respectively.

The third and sixth semiconductor layers 202 c and 204 c may also have agrowth rate lowest in the <111> crystal direction, and thus a growthrate in a direction substantially perpendicular to the upper surface ofthe substrate 100 may be much greater than the growth rate in the <111>crystal direction on the already formed {111} crystal plane.

Accordingly, a thickness of the third semiconductor layer 202 c on anupper side surface of the second semiconductor layer 202 b having the{111} crystal plane or a thickness of the sixth semiconductor layer 204c on an upper outer side surface of an outermost one of the secondshapes of the fifth semiconductor layer 204 b may be much less than athickness of the sixth semiconductor layer 204 c on an upper inner sidesurface of the outermost one of the second shapes of the fifthsemiconductor layer 204 b or a thickness of the sixth semiconductorlayer 204 c on upper side surfaces of other ones of the second shapes ofthe fifth semiconductor layer 204 b.

In some embodiments, the third SEG process may be performed until thethird and sixth semiconductor layers 202 c and 204 c may fill the thirdand fourth recesses 182 and 184, respectively, and the sixthsemiconductor layer 204 c may further grow above the fourth recess 184so that a top surface of the sixth semiconductor layer 204 c may behigher than a bottom of the second gate spacer 164. The sixthsemiconductor layer 204 c may fill a space between the second shapes ofpentagons of the fifth semiconductor layer 204 b, and may have an uppersurface whose central portion may be flat and higher that top surfacesof the second shapes. In some embodiments, the upper surface of thesixth semiconductor layer 204 c may be higher than a top surface of thethird semiconductor layer 202 c.

A fourth SEG process may be performed to form a first capping layer 212on the second and third semiconductor layers 202 b and 202 c and to forma second capping layer 214 on the fifth and sixth semiconductor layers204 b and 204 c. In some embodiments, the fourth SEG process may beperformed using a silicon source gas, an etching gas and a carrier gas,and thus a respective single crystalline silicon layer may be formed asthe first and second capping layers 212 and 214. In some embodiments,dichlorosilane (SiH₂Cl₂) gas may be used as the silicon source gas, andthus the first capping layer 212 may be formed on an upper side surfaceof the third semiconductor layer 202 c and on the lower side surface ofthe second semiconductor layer 202 b as well, and the second cappinglayer 214 may be formed on an upper side surface of the sixthsemiconductor layer 204 c and on the lower side surface of the fifthsemiconductor layer 204 b as well. However, the silicon source gas maynot be provided well onto an inner lower side surface of the outermostone of the second shapes of the fifth semiconductor layer 204 b or ontolower side surfaces of other ones of the second shapes of the fifthsemiconductor layer 204 b, and thus the second capping layer 214 may notbe formed thereon.

The first and second capping layers 212 and 214 may protect the first tothird semiconductor layers 202 a, 202 b and 202 c, and the fourth tosixth semiconductor layers 204 a, 204 b and 204 c, respectively, from aheat treatment subsequently performed, and in some embodiments, may notbe formed.

The first to third semiconductor layers 202 a, 202 b and 202 csequentially stacked on the first active fin 102 and the first cappinglayer 212 on the second and third semiconductor layers 202 b and 202 cmay form a first source/drain layer structure 222. Additionally, thefourth semiconductor layers 204 a on the respective second active fins104, the fifth semiconductor layer 204 b commonly contacting uppersurfaces of the fourth semiconductor layers 204 a, the sixthsemiconductor layer 204 c on the fifth semiconductor layer 204 b, andthe second capping layer 214 on the fifth and sixth semiconductor layers204 b and 204 c may form a second source/drain layer structure 224. Thefirst and second source/drain layer structures 222 and 224 may serve asa respective source/drain of a respective positive-channel metal oxidesemiconductor (PMOS) transistor.

In some embodiments, a top surface of the first source/drain layerstructure 222 may have a first height H1 from the upper surface of theisolation pattern 120, and an upper surface of the second source/drainlayer structure 224 may have a second height H2 from the upper surfaceof the isolation pattern 120, which may be greater than the first heightH1. The upper surface of the second source/drain layer structure 224 maybe constant along the second direction. Thus, the second source/drainlayer structure 224 may have a relatively large volume, and may apply asufficiently high compressive stress on a channel that may be formed ata portion of the second active fin 104 under the second dummy gatestructure, which may increase the mobility of holes.

The second source/drain layer structure 224 may include the sixthsemiconductor layer 204 c having a p-type impurity concentration greaterthan that of the fifth semiconductor layer 204 b, which may have a largevolume, and thus may have a low resistance. In the second source/drainlayer structure 224, the sixth semiconductor layer 204 c having arelatively high germanium concentration may be formed on the fifthsemiconductor layer 204 b having a relatively low germaniumconcentration, and thus the Schottky barrier of a second contact plug354 (refer to FIGS. 43 to 47 ) that is subsequently formed may decrease,and thus the contact resistance between the second source/drain layerstructure 224 and the second contact plug 354 may decrease.

The horizontal growth of the first source/drain layer structure 222 maybe reduced or prevented when the third semiconductor layer 202 c isformed on the second semiconductor layer 202 b, and thus neighboringones of the first source/drain layer structures 222 may not be mergedwith each other. Thus, the electrical short-circuit therebetween may beprevented.

Up to now, the first and second source/drain layer structures 222 and224 serving as the source/drain of the PMOS transistor have beendescribed, however, the inventive concepts may not be limited thereto,and the first and second source/drain layer structures 222 and 224 mayalso serve as a source/drain of a negative-channel metal oxidesemiconductor (NMOS) transistor.

Particularly, the first to third SEG processes may be formed using asilicon source gas, a carbon source gas, an etching gas and a carriergas, and thus respective a single crystalline silicon carbide layer maybe formed as the first to sixth semiconductor layers 202 a, 202 b, 202c, 204 a, 204 b and 204 c. In the first and second SEG processes, e.g.,silane (SiH₄) gas, disilane (Si₂H₆) gas, dichlorosilane (SiH₂Cl₂) gas,etc. may be used as the silicon source gas, e.g., monomethylsilane(SiH₃CH₃) gas may be used as the carbon source gas, e.g., hydrogenchloride (HCl) gas may be sued as the etching gas, and e.g., hydrogen(H₂) gas may be used as the carrier gas. In the third SEG process, e.g.,silane (SiH₄) gas and/or disilane (Si₂H₆) gas may be used as the siliconsource gas. Additionally, an n-type impurity source gas, e.g., phosphine(PH₃) gas may be also used to form a single crystalline silicon carbidelayer doped with n-type impurities.

In some embodiments, the first source/drain layer structure 222 may havea carbon concentration gradually increasing from the first semiconductorlayer 202 a through the second semiconductor layer 202 b toward thethird semiconductor layer 202 c therein, and also have an n-typeimpurity concentration gradually increasing from the first semiconductorlayer 202 a through the second semiconductor layer 202 b toward thethird semiconductor layer 202 c therein. Additionally, the secondsource/drain layer structure 224 may have a carbon concentrationgradually increasing from the fourth semiconductor layer 204 a throughthe fifth semiconductor layer 204 b toward the sixth semiconductor layer204 c therein, and also have an n-type impurity concentration graduallyincreasing from the fourth semiconductor layer 204 a through the fifthsemiconductor layer 204 b toward the sixth semiconductor layer 204 ctherein. Thus, the second source/drain layer structure 224 may apply asufficiently high tensile stress on a channel that may be formed at aportion of the second active fin 104 under the second dummy gatestructure, which may increase the mobility of electrons and theresistance.

Referring to FIGS. 25 and 26 , in some embodiments, the upper surface ofthe sixth semiconductor layer 204 c that may be formed by the third SEGprocess may be substantially coplanar with the top surface of the thirdsemiconductor layer 202 c. The upper surface of the sixth semiconductorlayer 204 c may be constant along the second direction.

That is, the third SEG process may be performed only until the sixthsemiconductor layer 204 c may fill the space between the second shapesof the fifth semiconductor layer 204 b, and thus the upper surface ofthe sixth semiconductor layer 204 c may be substantially coplanar with abottom of the second gate spacer 164. As a result, the second height H2of the second source/drain layer structure 224 may be constant, and maybe equal to the first height H1 of the first source/drain layerstructure 222. As used herein, a structure that is referred to as havinga height that is constant may have a surface that is substantially flatand substantially parallel to the surface of the substrate.

The second source/drain layer structure 224 that is described withreference to FIGS. 21 to 24 may include the sixth semiconductor layer204 c having a sufficiently large volume to apply sufficiently highstress on the channel, while a contact level between the secondsource/drain layer structure 224 and the second contact plug 354 that issubsequently formed may be relatively high so that a vertical length ofthe second contact plug 354 may be relatively short. Accordingly, acurrent path of current that is applied to the transistor may increasein the second source/drain layer structure 224 rather than in the secondcontact plug 354, which may deteriorate the performance of thetransistor.

However, in the second source/drain layer structure 224 shown in FIGS.25 and 26 , the upper surface of the sixth semiconductor layer 204 c maybe less high so that the second contact plug 354 that is subsequentlyformed on the sixth semiconductor layer 204 c may have a proper verticallength, even if the sixth semiconductor layer 204 c may fill the spacesbetween the second shapes of the fifth semiconductor layer 204 b. Thus,the performance of the transistor may not be deteriorated as compared tothe transistor of FIGS. 21 to 24 .

Further, referring to FIG. 27 , an upper surface of the sixthsemiconductor layer 204 c that may be formed by the third SEG processmay have a varying height. That is, the sixth semiconductor layer 204 cmay be conformally formed on the upper surface of the fifthsemiconductor layer 204 b, except for an area on the upper surface ofthe fifth semiconductor layer 204 b in which the second shapes of thefifth semiconductor layer 204 b meet each other. The sixth semiconductorlayer 204 c having the varying thickness may be formed by performing thethird SEG process for a short time period only. Thus, the second heightH2 of the top surface of the second source/drain layer structure 224 maybe substantially equal to the first height H1 of the top surface of thefirst source/drain layer structure 222, and the upper surface of thesecond source/drain layer structure 224 may be bent according to theshape of the upper surface of the fifth semiconductor layer 204 b.

The second source/drain layer structure 224 shown in FIG. 27 may beformed to increase a contact area between the second source/drain layerstructure 224 and the second contact plug 354 that is subsequentlyformed so that the contact resistance may be reduced, instead ofapplying the stress on the channel.

For example, the first to third SEG processes may be performed using asilicon source gas, an etching gas and a carrier gas, and thus arespective single crystalline silicon layer may be formed as the firstto sixth semiconductor layers 202 a, 202 b, 202 c, 204 a, 204 b and 204c. In the first and second SEG processes, e.g., silane (SiH₄) gas,disilane (Si₂H₆) gas, dichlorosilane (SiH₂Cl₂) gas, etc. may be used asthe silicon source gas, and in the third SEG process, e.g., silane(SiH₄) gas and/or disilane (Si₂H₆) gas may be used as the silicon sourcegas. Additionally, an n-type impurity source gas, e.g., phosphine (PH₃)gas may be also used to form a single crystalline silicon layer dopedwith n-type impurities.

The single crystalline silicon layer may have a lattice constantsubstantially equal to that of the substrate 100, and thus may not applya tensile stress on the NMOS transistor. Thus, the second source/drainlayer structure 224, i.e., the sixth semiconductor layer 204 c may nothave a large volume, and thus may be conformally formed on the fifthsemiconductor layer 204 b having a surface profile similar to that ofthe fifth semiconductor layer 204 b. Accordingly, the upper surface ofthe second source/drain layer structure 224 may be bent, and a contactarea with the second contact plug 354 may increase to reduce the contactresistance.

Hereinafter, for the convenience of explanation, only the first andsecond source/drain layer structures 222 and 224 serving as thesource/drain of the PMOS transistor will be described.

Referring to FIGS. 28 to 31 , an insulation layer 230 may be formed onthe first and second active fins 102 and 104 and the isolation pattern120 to cover the first and second dummy gate structures, the first andsecond gate spacers 162 and 164, and the first and second source/drainlayer structures 222 and 224 to a sufficient height, and may beplanarized until upper surfaces of the first and second dummy gateelectrodes 142 and 144 of the respective first and second dummy gatestructures may be exposed. In the planarization process, the first andsecond dummy gate masks 152 and 154 may be removed, and upper portionsof the first and second gate spacers 162 and 164 may be partiallyremoved. A space between the second source/drain layer structure 224 andthe isolation pattern 120 may not be filled with the insulation layer230, and thus an air gap 235 may be formed. The insulation layer 230 maybe formed of silicon oxide, e.g., tonen silazene (TOSZ). Theplanarization process may be performed by a chemical mechanicalpolishing (CMP) process and/or an etch back process.

Referring to FIGS. 32 to 35 , the exposed first and second dummy gateelectrodes 142 and 144 and the first and second dummy gate insulationpatterns 132 and 134 thereunder may be removed to form first and secondopenings that expose inner sidewalls of the respective first and secondgate spacers 162 and 164 and upper surfaces of the respective first andsecond active fins 102 and 104. First and second gate structures 282 and284 may be formed to fill the first and second openings, respectively.

Particularly, after performing a thermal oxidation process on the uppersurfaces of the first and second active fins 102 and 104 that areexposed by the respective first and second openings to form first andsecond interface patterns 242 and 244, respectively, a gate insulationlayer and a work function control layer may be sequentially formed onthe first and second interface patterns 242 and 244, the isolationpattern 120, the first and second gate spacers 162 and 164, and theinsulation layer 230, and a gate electrode layer may be formed on thework function control layer to sufficiently fill remaining portions ofthe first and second openings.

The gate insulation layer may be formed of a metal oxide having a highdielectric constant, e.g., hafnium oxide, tantalum oxide, zirconiumoxide, or the like, by a CVD process or an ALD process. The workfunction control layer may be formed of a metal nitride or a metalalloy, e.g., titanium nitride, titanium aluminum, titanium aluminumnitride, tantalum nitride, tantalum aluminum nitride, etc., and the gateelectrode layer may be formed of a material having a low electricalresistance, e.g., a metal such as aluminum, copper, tantalum, etc., or ametal nitride thereof. The work function control layer and the gateelectrode layer may be formed by an ALD process, a physical vapordeposition (PVD) process, or the like. In some embodiments, a heattreatment process, e.g., a rapid thermal annealing (RTA) process, aspike rapid thermal annealing (spike RTA) process, a flash rapid thermalannealing (flash RTA) process or a laser annealing process may befurther performed.

In some embodiments, the first and second interface patterns 242 and 244may be formed, instead of the thermal oxidation process, by a CVDprocess, an ALD process, or the like, similarly to the gate insulationlayer or the gate electrode layer. In such embodiments, the first andsecond interface patterns 242 and 244 may be formed not only on theupper surfaces of the respective first and second active fins 102 and104 but also on the upper surface of the isolation pattern 120 and theinner sidewalls of the respective first and second gate spacers 162 and164.

The gate electrode layer, the work function control layer, and the gateinsulation layer may be planarized until an upper surface of theinsulation layer 230 may be exposed to form a first gate insulationpattern 252 and a first work function control pattern 262 sequentiallystacked on the first interface pattern 242, the isolation pattern 120,and the inner sidewall of the first gate spacer 162, and a first gateelectrode 272 filling a remaining portion of the first opening on thefirst work function control pattern 262. Additionally, a second gateinsulation pattern 254 and a second work function control pattern 264may be sequentially stacked on the second interface pattern 244, theisolation pattern 120, and the inner sidewall of the second gate spacer164, and a second gate electrode 274 may be formed to fill a remainingportion of the second opening on the second work function controlpattern 264.

Accordingly, bottoms and sidewalls of the first and second gateelectrodes 272 and 274 may be covered by the first and second workfunction control patterns 262 and 264, respectively. In someembodiments, the planarization process may be performed by a CMP processand/or an etch back process.

The first interface pattern 242, the first gate insulation pattern 252,the first work function control pattern 262 and the first gate electrode272 sequentially stacked may form the first gate structure 282, and thefirst gate structure 282 together with the first source/drain layerstructure 222 may form a first transistor. Additionally, the secondinterface pattern 244, the second gate insulation pattern 254, thesecond work function control pattern 264 and the second gate electrode274 sequentially stacked may form the second gate structure 284, and thesecond gate structure 284 together with the second source/drain layerstructure 224 may form a second transistor. Each of the first and secondtransistors may be a PMOS transistor or an NMOS transistor according tothe conductivity type of each of the first and second source/drain layerstructures 222 and 224.

Referring to FIGS. 36 to 39 , a third capping layer 290 and aninsulating interlayer 300 may be sequentially formed on the insulationlayer 230, the first and second gate structures 282 and 284, and thefirst and second gate spacers 162 and 164. First and second contactholes 312 and 314 may be formed through the insulation layer 230, thethird capping layer 290 and the insulating interlayer 300 to exposeupper surfaces of the first and second source/drain layer structures 222and 224, respectively. The third capping layer 290 may be formed of anitride, e.g., silicon nitride, silicon oxynitride, siliconcarbonitride, silicon oxycarbonitride, etc., and the insulatinginterlayer 300 may be formed of silicon oxide, e.g., tetra ethyl orthosilicate (TEOS).

When the first and second contact holes 312 and 314 are formed, uppersurfaces of the first and second source/drain layer structures 222 and224 may be exposed, and further partially etched. Thus, the firstcontact hole 312 may extend through the first capping layer 212 and thethird semiconductor layer 202 c of the first source/drain layerstructure 222, and in some cases, may also extend through an upperportion of the second semiconductor layer 202 b.

In some embodiments, a semiconductor layer may be described as having across-sectional shape that is similar to a hexagon where an upperportion of the shape that was referred to as being similar to a pentagonis removed. Thus the shape that is similar to a hexagon may have fivesides, as described with respect to the shape that is similar to apentagon, and an additional top surface that is adjacent a respectivecontact hole. As discussed above with respect to the shape that issimilar to a pentagon, a bottom side of a shape that is similar to ahexagon may be partially or completely within other structures and theperimeter of the actual cross-sectional shape may contain additionalsides of structures that protrude into the shape that is similar to ahexagon.

The second contact hole 314 may extend through the second capping layer214 and the sixth semiconductor layer 204 c of the second source/drainlayer structure 224, and in some cases, may also extend through an upperportion of the fifth semiconductor layer 204 b. Alternatively, thesecond contact hole 314 may extend through only the second capping layer214 and the sixth semiconductor layer 204 c of the second source/drainlayer structure 224.

In some embodiments, ones of the first and second contact holes 312 and314 may have a flat bottom, and thus the bottom of ones of the first andsecond contact holes 312 and 314 may have a constant height. In someembodiments, the first and second contact holes 312 and 314 may havefirst and second depths D1 and D2, respectively, and the first depth D1may be greater than the second depth D2. An upper surface of the secondsource/drain layer structure 224 may be higher than that of the firstsource/drain layer structure 222, and thus the first contact hole 312may be formed to the first depth D1 greater than the second depth D2 ofthe second contact hole 314 due to an etching selectivity between theinsulating interlayer 300 and the source/drain layer structures 222 and224.

FIGS. 36 to 39 show that each of the first and second contact holes 312and 314 expose a central upper surface of each of the first and secondsource/drain layer structures 222 and 224 in the first direction,however, the inventive concepts may not be limited thereto. In someembodiments, the first and second contact holes 312 and 314 may beformed to be self-aligned with the first and second gate spacers 162 and164, respectively, and thus the first and second contact holes 312 and314 may expose an entire central upper surface of the respective firstand second source/drain layer structures 222 and 224.

Alternatively, referring to FIGS. 40 to 42 , ones of the first andsecond contact holes 312 and 314 may have a bent bottom, and thus thebottom of ones of the first and second contact holes 312 and 314 mayhave a varying height. That is, due to an etching selectivity betweenthe insulating interlayer 300 and the source/drain layer structures 222and 224, the first and second contact holes 312 and 314 may have bottomshapes similar to those of the upper surfaces of the first and secondsource/drain layer structures 222 and 224, respectively. Thus, in across-section taken along the second direction, the bottom of the firstcontact hole 312 may be bent and a central portion may be higher thanedge portions thereof. Additionally, in a cross-section taken along thesecond direction, a central portion of the bottom of the second contacthole 314 may be higher than edge portions of the bottom of the secondcontact hole 314, and the central portion may be substantially flat.

The first contact hole 312 may extend through the first capping layer212 and an upper portion of the third semiconductor layer 202 c of thefirst source/drain layer structure 222, and the second contact hole mayextend through the second capping layer 214 and an upper portion of thesixth semiconductor layer 204 c of the second source/drain layerstructure 224. Alternatively, the first contact hole 312 may extend onlythrough a portion of the first capping layer 212 of the firstsource/drain layer structure 222, and the second contact hole may extendonly through a portion of the second capping layer 214.

In some embodiments, the first depth D1 of the first contact hole 312,which may be a maximum depth of the first contact hole 312, may begreater than the second depth D2 of the second contact hole 314, whichmay be a maximum depth of the second contact hole 314, and a third depthD3 of the first contact hole 312, which may be a depth from an uppersurface of the insulating interlayer 300 to the central top surface ofthe first source/drain layer structure 222, may be greater than a fourthdepth D4 of the second contact hole 314, which may be a depth from theupper surface of the insulating interlayer 300 to the central uppersurface of the second source/drain layer structure 224.

Referring to FIGS. 43 to 47 , after forming a first metal layer on theexposed upper surfaces of the first and second source/drain layerstructures 222 and 224, sidewalls of the first and second contact holes312 and 314, and the upper surface of the insulating interlayer 300, aheat treatment process may be performed thereon to form first and secondmetal silicide patterns 322 and 324 on the first and second source/drainlayer structures 222 and 224, respectively. An unreacted portion of thefirst metal layer may be removed. The first metal layer may be formed ofa metal, e.g., titanium, cobalt, nickel, etc. The first metal silicidepattern 322 may include first, second and third portions 322 a, 322 band 322 c, and the second metal silicide pattern 324 may include fourth,fifth and sixth portions 324 a, 324 b and 324 c. Each of the germaniumconcentration and the p-type impurity concentration in the first metalsilicide pattern 322 may gradually increase from the first portionthrough the second portion to the third portion, and also each of thegermanium concentration and the p-type impurity concentration in thesecond metal silicide pattern 324 may gradually increase from the fourthportion through the fifth portion to the sixth portion.

A barrier layer may be formed on the first and second metal silicidepatterns 322 and 324, the sidewalls of the first and second contactholes 312 and 314 and the upper surface of the insulating interlayer300, a second metal layer may be formed on the barrier layer to fill thefirst and second contact holes 312 and 314, and the second metal layerand the barrier layer may be planarized until the upper surface of theinsulating interlayer 300 may be exposed. Thus, first and second contactplugs 352 and 354 may be formed on the first and second metal silicidepatterns 322 and 324 to fill the first and second contact holes 312 and314, respectively. The barrier layer may be formed of a metal nitride,e.g., titanium nitride, tantalum nitride, tungsten nitride, etc., andthe second metal layer may be formed of a metal, e.g., tungsten, copper,etc. The first contact plug 352 may include a first metal pattern 342and a first barrier pattern 332 covering a bottom and a sidewallthereof, and the second contact plug 354 may include a second metalpattern 344 and a second barrier pattern 334 covering a bottom and asidewall thereof.

In some embodiments, ones of the first and second contact plugs 352 and354 may have a flat bottom, and thus the bottom of ones of the first andsecond contact plugs 352 and 354 may have a constant height. In someembodiments, the first and second contact plugs 352 and 354 may havefirst and second lengths L1 and L2, respectively, along a directionsubstantially perpendicular to the upper surface of the substrate 100,and the first length L1 may be greater than the second length L2. Awiring and a via may be further formed to be electrically connected tothe first and second contact plugs 352 and 354 to complete thesemiconductor device.

FIGS. 48 to 50 show that the first and second contact plugs 352 and 354may be formed on the first and second source/drain layer structures 222and 224, respectively, that are described with reference to FIGS. 25 and26 . For example, the top surface of the first source/drain layerstructure 222 may be substantially coplanar with the upper surface ofthe second source/drain layer structure 224, and thus the first andsecond lengths L1 and L2 of the respective first and second contactplugs 352 and 354 contacting the first and second source/drain layerstructures 222 and 224, respectively, may be substantially equal to eachother.

FIGS. 51 to 53 show that the first and second contact plugs 352 and 354may be formed on the first and second source/drain layer structures 222and 224, respectively, that are described with reference to FIG. 27 .For example, the top surface of the second source/drain layer structure224 may be substantially coplanar with the top surface of the firstsource/drain layer structure 222. However, the upper surface of thesecond source/drain layer structure 224 may have a varying height. Thus,the second length L2 of the second contact plug 354 contacting thesecond source/drain layer structure 224 may be similar to the firstlength L1 of the first contact plug 352 contacting the firstsource/drain layer structure 222, however, the second contact plug 354may have a fifth length L5 greater than the first length L1 at a portionthereof. The upper surface of the second source/drain layer structure224 and the bottom of the second contact plug 354 may be bent, and thusthe contact area between the second source/drain layer structure 224 andthe second contact plug 354 may increase to reduce the contactresistance.

FIGS. 54 to 56 show the first and second contact plugs 352 and 354filling the first and second contact holes 312 and 314, respectively.Thus, ones of the first and second contact plugs 352 and 354 may have abent bottom, and the bottom of ones of the first and second contactplugs 352 and 354 may have a varying height. In some embodiments, in across-section taken along the second direction, the bottom of the firstcontact plug 352 may be bent and have a central portion higher than edgeportions thereof, and in a cross-section taken along the seconddirection, the bottom of the second contact plug 354 may have a flatcentral portion higher than edge portions thereof.

In some embodiments, the first length L1 of the first contact plug 352,which may be the maximum length of the first contact plug 352, may begreater than the second length L2, which may be the maximum length ofthe second contact plug 354, and a third length L3 of the first contactplug 352, which may be a length of the first contact plug 352 from anupper surface thereof to the central upper surface of the firstsource/drain layer structure 222, may be greater than a fourth length L4of the second contact plug 354, which may be a length of the secondcontact plug 354 from an upper surface thereof to the central uppersurface of the second source/drain layer structure 224.

FIGS. 57 and 58 show the first and second contact plugs 352 and 354filling the first and second contact holes 312 and 314, respectively,that are described with reference to FIGS. 40 to 42 that may expose theupper surfaces of the first and second source/drain layer structures 222and 224 that are described with reference to FIGS. 25 and 26 . In someembodiments, the first length L1 of the first contact plug 352, whichmay be the maximum length of the first contact plug 352, may besubstantially equal to the second length L2, which may be the maximumlength of the second contact plug 354, and the third length L3 of thefirst contact plug 352, which may be the length of the first contactplug 352 from the upper surface thereof to the central upper surface ofthe first source/drain layer structure 222, may be substantially equalto the fourth length L4 of the second contact plug 354, which may be thelength of the second contact plug 354 from the upper surface thereof tothe central upper surface of the second source/drain layer structure224.

FIG. 59 shows a semiconductor device including the isolation pattern 120that is described with reference to FIG. 16 .

As described above, in the method of manufacturing the semiconductordevice, when the first and second source/drain layer structures 222 and224 are formed in the first and second regions I and II, respectively,of the substrate 100, the SEG process may be performed using silane(SiH₄) gas and/or disilane (Si₂H₆) gas as a silicon source gas underproper process conditions so that the third and sixth semiconductorlayers 202 c and 204 c may be formed on the second and fifthsemiconductor layers 202 b and 204 b, respectively. Thus, the horizontalgrowth of the third and sixth semiconductor layers 202 c and 204 c maybe prevented. Accordingly, the first source/drain layer structures 222that may be formed on neighboring ones of the first active fins 102 maynot be merged with each other, and the second source/drain layerstructure 224 commonly contacting the upper surfaces of neighboring onesof the second active fins 104 may have a desired volume. Thus, theelectrical failure of the first transistors, e.g., pull-up transistorsof an SRAM device may be prevented in the first region I, while a properstress may be applied to a channel of the second transistor and thesecond transistor may have good performance.

FIGS. 60 to 100 are plan views and cross-sectional views schematicallyillustrating intermediate operations of methods of manufacturingsemiconductor devices according to some embodiments. Particularly, FIGS.60, 62, 65, 69, 73, 78, 84, 89 and 94 are plan views, and FIGS. 61,63-64, 66-68, 70-72, 74-77, 79-83, 85-88, 90-93 and 95-100 arecross-sectional views.

FIGS. 61, 66, 70, 74, 79, 81, 83, 90, 95 and 100 are cross-sectionalviews taken along lines A-A′ of corresponding plan views, respectively.FIGS. 63, 85 and 96 are cross-sectional views taken along lines B-B′ ofcorresponding plan views, respectively. FIGS. 64, 67, 71, 75, 86, 91 and97 are cross-sectional views taken along lines C-C′ of correspondingplan views, respectively. FIGS. 72, 76, 87, 92 and 98 arecross-sectional views taken along lines D-D′ of corresponding planviews, respectively. and FIGS. 68, 77, 80, 82, 88, 93 and 99 arecross-sectional views taken along lines E-E′ of corresponding planviews, respectively.

The methods of manufacturing semiconductor devices that are illustratedin FIGS. 60-100 may include processes that are substantially the same asor similar to those that are described with reference to FIGS. 1 to 59 .Thus, like reference numerals refer to like elements, and detaileddescriptions thereon may be omitted herein for brevity.

Referring to FIGS. 60 and 61 , processes that are substantially the sameas or similar to those that are described with reference to FIGS. 1 and2 may be performed. Thus, an upper portion of a substrate 100 may bepartially etched to form first, second and third recesses 412, 414 and416. The substrate 100 may include first, second and third regions I, IIand III. In some embodiments, the first region I may serve as an SRAMregion in which SRAM devices may be formed, and the second and thirdregions II and III may serve as logic regions in which logic devices maybe formed. The second and third regions II and III may be PMOS and NMOSregions, respectively. The first region I may be a PMOS region or anNMOS region, however, for the convenience of explanation, the firstregion I serving as the PMOS region will be described hereinafter.

Alternatively, any of the first to third regions I, II and III may be alogic region or a peripheral circuit region, however, a width of a firstrecess 412 in the first region I may be greater than widths of secondand third recesses 414 and 416 in the second and third region II andIII, respectively.

As the first to third recesses 412, 414 and 416 are formed on thesubstrate 400, first, second and third active regions 402, 404 and 406may be defined in the first, second and third regions I, II and III,respectively, of the substrate 400.

In some embodiments, the first to third active regions 402, 404 and 406may extend in a first direction substantially parallel to an uppersurface of the substrate 400, and a plurality of first active fins 402,a plurality of second active fins 404 and a plurality of third activefins 406 may be formed in a second direction, which may be substantiallyparallel to the upper surface of the substrate 100 and cross the firstdirection. In some embodiments, the first and second directions maycross each other at a right angle, and thus may be substantiallyperpendicular to each other.

In some embodiments, a distance between the first active fins 402 in thesecond direction may be greater than a distance between the secondactive fins 404 in the second direction and greater than a distancebetween the third active fins 406 in the second direction.

Referring to FIGS. 62 and 64 , processes that are substantially the sameas or similar to those that are described with reference to FIGS. 4 to 8may be performed. Thus, an isolation pattern 420 may be formed on thesubstrate 400 to fill lower portions of the first to third recesses 412,414 and 416. The first active fin 402 may include a first lower activepattern 402 b whose sidewall may be covered by the isolation pattern420, and a first upper active pattern 402 a that is not covered by theisolation pattern 420 but protruding therefrom, the second active fin404 may include a second lower active pattern 404 b whose sidewall maybe covered by the isolation pattern 420, and a second upper activepattern 404 a that is not covered by the isolation pattern 420 butprotruding therefrom, and the third active fin 406 may include a thirdlower active pattern 406 b whose sidewall may be covered by theisolation pattern 420, and a third upper active pattern 406 a that isnot covered by the isolation pattern 420 but protruding therefrom.

Additionally, first to third dummy gate structures may be formed on thefirst to third regions I, II and III, respectively, of the substrate400. The first dummy gate structure may include a first dummy gateinsulation pattern 432, a first dummy gate electrode 442 and the firstdummy gate mask 452 sequentially stacked on the first region I of thesubstrate 400, the second dummy gate structure may include a seconddummy gate insulation pattern 434, a second dummy gate electrode 444 andthe second dummy gate mask 454 sequentially stacked on the second regionII of the substrate 400, and the third dummy gate structure may includea third dummy gate insulation pattern 436, a third dummy gate electrode446 and the third dummy gate mask 456 sequentially stacked on the thirdregion III of the substrate 400.

In some embodiments, the first to third dummy gate structures may beformed to extend in the second direction, and a plurality of first dummygate structures, a plurality of second dummy gate structures, and aplurality of third dummy gate structures may be formed in the firstdirection.

Referring to FIGS. 65 to 68 , processes similar to those that aredescribed with reference to FIGS. 9 to 11 may be performed. That is, afirst spacer layer 460 may be formed on the first to third regions I, IIand III of the substrate 400 having the first and second dummy gatestructures thereon, a first photoresist pattern 10 may be formed tocover the third region III of the substrate 400, and an anisotropicetching process may be performed using the first photoresist pattern 10as an etching mask.

Thus, in the first region I of the substrate 400, a first gate spacer462 may be formed on opposite sidewalls of the first dummy gatestructure in the first direction, and a first fin spacer 472 may be alsoformed on opposite sidewalls of the first active fin 402 in the seconddirection. Additionally, in the second region II of the substrate 400, asecond gate spacer 464 may be formed on opposite sidewalls of the seconddummy gate structure in the first direction, and a second fin spacer 474may be also formed on opposite sidewalls of the second active fin 404 inthe second direction.

Referring to FIGS. 69 to 72 , processes similar to those that aredescribed with reference to FIGS. 12 to 24 may be performed.

That is, after removing the first photoresist pattern 10, an upperportion of the first active fin 402 adjacent the first dummy gatestructure may be etched to form a fourth recess, and an upper portion ofthe second active fin 404 adjacent the second dummy gate structure maybe etched to form a fifth recess. Particularly, the upper portions ofthe first and second active fins 402 and 404 may be removed using thefirst and second dummy gate structures and the first and second gatespacers 462 and 464 on sidewalls thereof in the first and second regionsI and II, respectively, as an etching mask to form the fourth and fifthrecesses. The first and second fin spacers 472 and 474 may be alsoremoved, and the third active fin 406 may not be etched because thefirst spacer layer 460 may remain in the third region III of thesubstrate 400.

First to fourth SEG processes may be performed to form first and secondsource/drain layer structures 522 and 524 on the first and second activefins 402 and 404 to fill the fourth and fifth recesses, respectively.The first source/drain layer structure 522 may include first to thirdsemiconductor layers 502 a, 502 b and 502 c that are sequentiallystacked on the first active fin 402, and a first capping layer 512 onthe second and third semiconductor layers 502 b and 502 c. Additionally,the second source/drain layer structure 524 may include fourthsemiconductor layers 504 a on the respective second active fins 404, afifth semiconductor layer 504 b commonly contacting upper surfaces ofthe fourth semiconductor layers 504 a, a sixth semiconductor layer 504 con the fifth semiconductor layer 504 b, and a second capping layer 514on the fifth and sixth semiconductor layers 504 b and 504 c.

Each of the first to fourth SEG processes may be performed using asilicon source gas, a germanium source gas, an etching gas, a carriergas and a p-type impurity source gas, so that a single crystallinesilicon-germanium layer doped with p-type impurities may be formed toserve as a source/drain of a PMOS transistor.

In some embodiments, a top surface of the first source/drain layerstructure 522 may have a first height H1 from an upper surface of theisolation pattern 420, and an upper surface of the second source/drainlayer structure 524 may have a second height H2 from the upper surfaceof the isolation pattern 420, which may be greater than the first heightH1. The upper surface of the second source/drain layer structure 524 maybe constant along the second direction. Thus, the second source/drainlayer structure 524 may have a relatively large volume, and may apply asufficiently high compressive stress on a channel that may be formed ata portion of the second active fin 404 under the second dummy gatestructure, which may increase the mobility of holes.

The second source/drain layer structure 524 may include the sixthsemiconductor layer 504 c having a p-type impurity concentration greaterthan that of the fifth semiconductor layer 504 b, which may have a largevolume, and thus may have a low resistance. Additionally, in the secondsource/drain layer structure 524, the sixth semiconductor layer 504 chaving a relatively high germanium concentration may be formed on thefifth semiconductor layer 504 b having a relatively low germaniumconcentration, and thus the contact resistance between the secondsource/drain layer structure 524 and a second contact plug 654 (refer toFIGS. 94 to 99 ) subsequently formed may decrease.

The horizontal growth of the first source/drain layer structure 522 maybe reduced or prevented when the third semiconductor layer 502 c isformed on the second semiconductor layer 502 b, and thus neighboringones of the first source/drain layer structures 522 may not be mergedwith each other. Thus, the electrical short-circuit therebetween may beprevented.

Alternatively, the second source/drain layer structure 524 may be formedto have shapes that are described with reference to FIGS. 25 to 27 .

Referring to FIGS. 73 to 77 , processes similar to those that aredescribed with reference to FIGS. 9 to 11 may be performed again. Thatis, a second spacer layer 465 may be formed on the first to thirdregions I, II and III of the substrate 400 having the first and seconddummy gate structures, the first and second gate spacers 462 and 464,the first and second source/drain layer structures 522 and 524 and thefirst spacer layer 460 thereon, a second photoresist pattern 20 may beformed on the first and second dummy gate structures, the first andsecond gate spacers 462 and 464, and the first and second source/drainlayer structures 522 and 524 to cover the first and second regions I andII of the substrate 400, and an anisotropic etching process may beperformed using the second photoresist pattern 20 as an etching mask.

Thus, in the third region III of the substrate 400, a third gate spacerstructure 468 may be formed on opposite sidewalls of the first dummygate structure in the first direction, and a third fin spacer structure478 may be also formed on opposite sidewalls of the third active fin 406in the second direction. The third gate spacer structure 468 may includethird and fourth spacers 463 and 467 sequentially stacked on thesidewalls of the third dummy gate structure, and the third fin spacerstructure 478 may include third and fourth fin spacers 473 and 477sequentially stacked on the sidewalls of the third active fin 406.

In some embodiments, the second spacer layer 465 may be formed of amaterial that is substantially the same as that of the first spacerlayer 460, and thus the second spacer layer 465 may be merged with thefirst and second gate spacers 462 and 464 in the first and secondregions I and II of the substrate 400, and may be merged with the firstspacer layer 460 in the third region III of the substrate 400.

Referring to FIGS. 78 to 80 , processes similar to those that aredescribed with reference to FIGS. 12 to 24 may be performed again. Thatis, after removing the second photoresist pattern 20, an upper portionof the third active fin 406 adjacent the third dummy gate structure maybe etched to form a sixth recess. Particularly, an upper portion of thethird active fin 406 may be removed using the third dummy gate structureand the third gate spacer structure 468 on sidewalls thereof in thethird region III, as an etching mask to form the sixth recess. The thirdfin spacer structure 478 may be also removed, and the first and secondsource/drain layer structures 522 and 524 may not be etched because thesecond spacer layer 465 may remain in the first and second regions I andII of the substrate 400.

First to fourth SEG processes may be performed again to form a thirdsource/drain layer structure 526 on the third active fins 406 to fillthe sixth recess. The third source/drain layer structure 526 may includeseventh semiconductor layers 506 a on the respective third active fins406, an eighth semiconductor layer 506 b commonly contacting uppersurfaces of the seventh semiconductor layers 506 a, a ninthsemiconductor layer 506 c on the eighth semiconductor layer 506 b, and athird capping layer 516 on the eighth and ninth semiconductor layers 506b and 506 c.

In some embodiments, the first to fourth SEG processes may be performedusing a silicon source gas, a carbon source gas, an etching gas, acarrier gas and an n-type impurity source gas, so that a singlecrystalline silicon carbide layer doped with n-type impurities may beformed to serve as a source/drain of an NMOS transistor.

In some embodiments, a top surface of the third source/drain layerstructure 526 may have a third height H1 from an upper surface of theisolation pattern 420, which may be greater than the first height H1.The upper surface of the third source/drain layer structure 526 may beconstant along the second direction. Thus, the third source/drain layerstructure 526 may have a relatively large volume, and may apply asufficiently high tensile stress on a channel that may be formed at aportion of the third active fin 406 under the third dummy gatestructure, which may increase the mobility of electrons. The thirdheight H3 may be substantially equal to or different from the secondheight H2.

Referring to FIGS. 81 and 82 , the third source/drain layer structure526 may be formed to have a shape that is described with reference toFIGS. 25 and 26 . Referring to FIG. 83 , the third source/drain layerstructure 526 may be formed to have a shape that is described withreference to FIG. 27 . The third source/drain layer structures 526 thatare described with reference to FIGS. 81 to 83 may be formed byperforming the first to fourth SEG processes using a silicon source gas,an etching gas, a carrier gas and an n-type impurity source gas, andthus a single crystalline silicon layer doped with n-type impurities maybe formed.

Referring to FIGS. 84 to 88 , processes that are substantially the sameas or similar to those that are described with reference to FIGS. 28 to35 may be performed. Thus, an insulation layer 530 may be formed on thefirst to third active fins 402, 404 and 406 and the isolation pattern420 to cover the first to third dummy gate structures, the first andsecond gate spacers 462 and 464, the second spacer layer 465, the thirdgate spacer structure 468, and the first to third source/drain layerstructures 522, 524 and 526 to a sufficient height, and may beplanarized until upper surfaces of the first to third dummy gateelectrodes 442, 444 and 446 of the respective first to third dummy gatestructures may be exposed.

In the planarization process, the first to third dummy gate masks 452,454 and 456 may be removed, and the second spacer layer 465 and upperportions of the third gate spacer structure 468 may be partiallyremoved. The second spacer layer 465 may be partially removed so thatportions of the second spacer layer 465 may remain in the first andsecond regions I and II, respectively, and hereinafter, which may bereferred to as fifth and sixth gate spacers 465 a and 465 b,respectively. Thus, the first and fifth gate spacers 462 and 465 a inthe first region I may form a first gate spacer structure 466, and thesecond and sixth gate spacers 464 and 465 b in the second region II mayform a second gate spacer structure 469.

The exposed first to third dummy gate electrodes 442, 444 and 446 andthe first to third dummy gate insulation patterns 432, 434 and 436thereunder may be removed to form first to third openings that exposeinner sidewalls of the respective first to third gate spacer structures466, 469 and 468 and upper surfaces of the respective first to thirdactive fins 402, 404 and 406, and first to third gate structures 582,584 and 586 may be formed to fill the first to third openings,respectively.

The first gate structure may include a first interface pattern 542, afirst gate insulation pattern 552, a first work function control pattern562 and a first gate electrode 572 sequentially stacked, and the firstgate structure 582 together with the first source/drain layer structure522 may form a first transistor. The second gate structure may include asecond interface pattern 544, a second gate insulation pattern 554, asecond work function control pattern 564 and a second gate electrode 574sequentially stacked, and the second gate structure 584 together withthe second source/drain layer structure 524 may form a secondtransistor. The third gate structure may include a third interfacepattern 546, a third gate insulation pattern 556, a third work functioncontrol pattern 566 and a third gate electrode 576 sequentially stacked,and the third gate structure 586 together with the third source/drainlayer structure 526 may form a third transistor. The first and secondtransistors may be PMOS transistors and the third transistor may be anNMOS transistor. In some embodiments, the first transistor may be anNMOS transistor.

Referring to FIGS. 89 to 93 , processes that are substantially the sameas or similar to those that are described with reference to FIGS. 36 to39 may be performed. Thus, a fourth capping layer 590 and an insulatinginterlayer 600 may be sequentially formed on the insulation layer 530,the first to third gate structures 582, 584 and 586, and the first tothird gate spacer structures 466, 469 and 468, and first to thirdcontact holes 612, 614 and 616 may be formed through the insulationlayer 530, the fourth capping layer 590 and the insulating interlayer600 to expose upper surfaces of the first to third source/drain layerstructures 522, 524 and 526, respectively. When the first to thirdcontact holes 612, 614 and 616 are formed, the upper surfaces of thefirst to third source/drain layer structures 522, 524 and 526 may beexposed, and further partially etched.

In some embodiments, ones of the first to third contact holes 612, 614and 616 may have a flat bottom, and thus the bottom of ones of the firstto third contact holes 612, 614 and 616 may have a constant height.Alternatively, like the processes that are described with reference toFIGS. 40 to 42 , ones of the first to third contact holes 612, 614 and616 may have a bent bottom, and thus the bottom of ones of the first tothird contact holes 612, 614 and 616 may have a varying height.

In some embodiments, the first to third contact holes 612, 614 and 616may have first to third depths D1, D2 and D3, respectively, and thefirst depth D1 may be greater than the second and third depths D2 andD3. The second and third depths D2 and D3 may be substantially equal toor different from each other.

Referring to FIGS. 94 to 99 , processes that are substantially the sameas or similar to those that are described with reference to FIGS. 43 to47 may be performed to complete the semiconductor device. That is, afterforming a first metal layer on the exposed upper surfaces of the firstto third source/drain layer structures 522, 524 and 526, sidewalls ofthe first to third contact holes 612, 614 and 616, and the upper surfaceof the insulating interlayer 600, a heat treatment process may beperformed thereon to form first to third metal silicide patterns 622,624 and 626 on the first to third source/drain layer structures 522, 524and 526, respectively. An unreacted portion of the first metal layer maybe removed. The first metal layer may be formed of a metal, e.g.,titanium, cobalt, nickel, etc. The first metal silicide pattern 622 mayinclude first, second and third portions 622 a, 622 b and 622 c, thesecond metal silicide pattern 624 may include fourth, fifth and sixthportions 624 a, 624 b and 624 c, and the third metal silicide pattern626 may include seventh, eighth and ninth portions 626 a, 626 b and 626c.

First to third contact plugs 652, 654 and 656 may be formed on the firstto third metal silicide patterns 622, 624 and 626 to fill the first tothird contact holes 612, 614 and 616, respectively. The first contactplug 652 may include a first metal pattern 642 and a first barrierpattern 632 covering a bottom and a sidewall thereof, the second contactplug 654 may include a second metal pattern 644 and a second barrierpattern 634 covering a bottom and a sidewall thereof, and the thirdcontact plug 656 may include a third metal pattern 646 and a thirdbarrier pattern 636 covering a bottom and a sidewall thereof.

In some embodiments, ones of the first to third contact plugs 652, 654and 656 may have a flat bottom, and thus the bottom of ones of the firstto third contact plugs 652, 654 and 656 may have a constant height.Alternatively, when the first to third contact plugs 652, 654 and 656fill the first to third contact holes 612, 614 and 616, respectively,having the shapes that are described with reference to FIGS. 40 to 42 ,ones of the first to third contact plugs 652, 654 and 656 may have abent bottom, and thus the bottom of ones of the first to third contactplugs 652, 654 and 656 may have a varying height.

In some embodiments, the first to third contact plugs 652, 654 and 656may have first, second and sixth lengths L1, L2 and L6, respectively,along a direction substantially perpendicular to the upper surface ofthe substrate 400, and the first length L1 may be greater than thesecond and sixth lengths L2 and L6. The second and sixth lengths L2 andL6 may be substantially equal to or different from each other.

Alternatively, at least one of the second and third contact plugs 654and 656 may have the shape that is described with reference to FIGS. 48to 50 , and in this case, at least one of the second and sixth lengthsL2 and L6 may be substantially equal to the first length L1.

FIG. 100 shows that the third contact plug 656 may have the shape thatis described with reference to FIGS. 51 to 53 , and a portion of thethird contact plug 656 may have a seventh length L7 greater than thefirst length L1. That is, the upper surface of the third source/drainlayer structure 526 and the bottom of the third contact plug 656 may bebent, and thus the contact area therebetween may increase to reduce thecontact resistance. The third source/drain layer structure 526 may havea multi-layered structure including a plurality of single crystallinesilicon layers doped with n-type impurities.

A wiring and a via may be further formed to be electrically connected tothe first to third contact plugs 652, 654 and 656.

The above method of manufacturing the semiconductor device may beapplied to methods of manufacturing various types of memory devicesincluding source/drain layers that may be formed by an SEG process. Forexample, the method may be applied to methods of manufacturing logicdevices such as central processing units (CPUs), main processing units(MPUs), or application processors (APs), or the like. Additionally, themethod may be applied to methods of manufacturing volatile memorydevices such as DRAM devices or SRAM devices, or non-volatile memorydevices such as flash memory devices, PRAM devices, MRAM devices, RRAMdevices, or the like.

The foregoing is illustrative of some embodiments of the inventiveconcepts and is not to be construed as limiting thereof. Although someembodiments have been described, those skilled in the art will readilyappreciate that many modifications are possible without materiallydeparting from the novel teachings and advantages of the presentinventive concepts. Accordingly, all such modifications are intended tobe included within the scope of the present inventive concepts asdefined in the claims. In the claims, means-plus-function clauses areintended to cover the structures described herein as performing therecited function and not only structural equivalents but also equivalentstructures. Therefore, it is to be understood that the foregoing isillustrative of some embodiments and is not to be construed as limitedto the specific embodiments disclosed, and that modifications to thedisclosed embodiments, as well as other embodiments, are intended to beincluded within the scope of the appended claims.

What is claimed is:
 1. A method of manufacturing a semiconductor device,the method comprising: forming an isolation pattern on a surface of asubstrate, the isolation pattern on lower portions of a first active finand a plurality of second active fins, the substrate comprising firstand second regions, wherein the first and second active fins are in thefirst and second active regions, respectively; forming first and seconddummy gate structures on the first and second active fins, respectively;forming first and second source/drain layer structures, by a selectiveepitaxial growth (SEG) process, on portions of the first and secondactive fins that are adjacent the first and second gate structures,respectively, wherein the second source/drain layer structure commonlycontacts upper surfaces of the second active fins, and a top surface ofthe second source/drain layer structure is farther from the surface ofthe substrate than a top surface of the first source/drain layerstructure is to the surface of the substrate; and replacing the firstand second dummy gate structures with first and second gate structures,respectively.
 2. The method of claim 1, wherein forming the first andsecond source/drain layer structures comprises: forming first and secondrecesses by etching upper portions of the first and second active finsthat are adjacent the first and second dummy gate structures,respectively; and forming the first and second source/drain layerstructures in the first and second recesses, respectively.
 3. The methodof claim 2, wherein the SEG process comprises using a silicon sourcegas, a germanium source gas and/or hydrogen chloride (HCl) gas.
 4. Themethod of claim 3, wherein the silicon source gas comprises silane(SiH₄) gas and/or disilane (Si₂H₆) gas.
 5. The method of claim 3,wherein the SEG process that forms the first and second source/drainlayer structures comprises: a first SEG process comprising providing thesilicon source gas and the germanium source gas with respective firstand second flow rates to form first and fourth semiconductor layers inthe respective first and second recesses; a second SEG processcomprising providing the silicon source gas and the germanium source gaswith respective third and fourth flow rates to form second and fifthsemiconductor layers on the respective first and fourth semiconductorlayers; and a third SEG process comprising providing the silicon sourcegas and the germanium source gas with respective fifth and sixth flowrates to form third and sixth semiconductor layers in the respectivesecond and fifth semiconductor layers.
 6. The method of claim 5, whereinthe second SEG process forms the second and fifth semiconductor layershaving a {111} crystal plane, and wherein the third SEG process formsthe third and sixth semiconductor layers on upper sidewall surfaces ofthe respective second and fifth semiconductor layers facing away fromthe substrate and not on lower sidewall surfaces of the respectivesecond and fifth semiconductor layers facing towards the substrate. 7.The method of claim 6, wherein a cross-section of the secondsemiconductor layer taken along a direction that is substantiallyparallel to the surface of the substrate and parallel to the first andsecond gate structures has a first shape comprising upper sidewallsurfaces defining an angle with respect to the surface of the substrateand facing away from the substrate and lower sidewall surfaces definingan angle with respect to the surface of the substrate and facing towardsthe surface of the substrate, wherein the third semiconductor layer ison the upper sidewall surfaces of the second semiconductor layer,wherein a cross-section of the fifth semiconductor layer taken along thedirection has a shape comprising a plurality of second shapes that areconnected to each other in the direction, the second shapes being onrespective ones of the second active fins and comprising upper sidewallsurfaces defining an angle with respect to the surface of the substrateand facing away from the substrate, lower sidewall surfaces defining anangle with respect to the surface of the substrate and facing towardsthe surface of the substrate, and a top surface that is parallel to thesurface of the substrate, and wherein the sixth semiconductor layer ison the upper sidewall surfaces of the fifth semiconductor layer.
 8. Themethod of claim 5, further comprising, after performing the third SEGprocess, performing a fourth SEG process comprising providingdichlorosilane (SiH₂Cl₂) gas to form first and second silicon layers onthe third and sixth semiconductor layers, respectively.
 9. The method ofclaim 2, wherein the SEG process comprises using a silicon source gas, acarbon source gas and/or hydrogen chloride (HCl) gas.
 10. The method ofclaim 9, wherein the silicon source gas comprises silane (SiH₄) gasand/or disilane (Si₂H₆) gas.
 11. The method of claim 9, wherein the SEGprocess that forms the first and second source/drain layer structurescomprises: a first SEG process comprising providing the silicon sourcegas and the carbon source gas with respective first and second flowrates to form first and fourth semiconductor layers in the respectivefirst and second recesses; a second SEG process comprising providing thesilicon source gas and the carbon source gas with respective third andfourth flow rates to form second and fifth semiconductor layers on therespective first and fourth semiconductor layers; and a third SEGprocess comprising providing the silicon source gas and the carbonsource gas with respective fifth and sixth flow rates to form third andsixth semiconductor layers in the respective second and fifthsemiconductor layers.
 12. The method of claim 1, further comprising:after forming the first and second source/drain layer structures,forming an insulating interlayer on the first and second source/drainlayer structures and sidewalls of the first and second dummy gatestructures; after replacing the first and second dummy gate structureswith the first and second gate structures, partially etching theinsulating interlayer to form first and second contact holes that exposeupper surfaces of the first and second source/drain layer structures;and forming first and second contact plugs in the first and secondcontact holes, respectively.
 13. The method of claim 12, furthercomprising: after forming the first and second contact holes, formingfirst and second metal silicide patterns on the first and secondsource/drain layer structures exposed by the first and second contactholes, respectively.
 14. A method of manufacturing a semiconductordevice, the method comprising: forming an isolation pattern on a surfaceof a substrate, the isolation pattern on lower portions of a firstactive fin and a plurality of second active fins, the substratecomprising first and second regions, and the first and second activefins in the first and second active regions, respectively; forming firstand second dummy gate structures on the first and second active fins,respectively; forming first and second source/drain layer structures, bya selective epitaxial growth (SEG) process, on portions of the first andsecond active fins that are adjacent the first and second gatestructures, respectively, the second source/drain layer structurecommonly contacting upper surfaces of the second active fins, and a topsurface of the second source/drain layer structure being substantiallycoplanar with a top surface of the first source/drain layer structure;replacing the first and second dummy gate structures with first andsecond gate structures, respectively; forming a first contact plug onthe first source/drain layer structure; and forming a second contactplug on the second source/drain layer structure, a bottom of the secondcontact plug being substantially flat and substantially parallel to thesurface of the substrate.
 15. The method of claim 14, wherein formingthe first and second source/drain layer structures comprises: formingfirst and second recesses by etching upper portions of the first andsecond active fins that are adjacent the first and second dummy gatestructures, respectively, wherein the SEG process comprises using asilicon source gas, a germanium source gas and/or hydrogen chloride(HCl) gas to form the first and second source/drain layer structures inthe first and second recesses, respectively, wherein the silicon sourcegas comprises silane (SiH₄) gas and/or disilane (Si₂H₆) gas.
 16. Themethod of claim 15, wherein the SEG process that forms the first andsecond source/drain layer structures comprises: a first SEG processcomprising providing the silicon source gas and the germanium source gaswith respective first and second flow rates to form first and fourthsemiconductor layers in the respective first and second recesses; asecond SEG process comprising providing the silicon source gas and thegermanium source gas with respective third and fourth flow rates to formsecond and fifth semiconductor layers on the respective first and fourthsemiconductor layers; and a third SEG process comprising providing thesilicon source gas and the germanium source gas with respective fifthand sixth flow rates to form third and sixth semiconductor layers in therespective second and fifth semiconductor layers.
 17. The method ofclaim 16, wherein the second SEG process forms the second and fifthsemiconductor layers having a {111} crystal plane, and wherein the thirdSEG process forms the third and sixth semiconductor layers on uppersidewall surfaces of the respective second and fifth semiconductorlayers facing away from the substrate and not on lower sidewall surfacesof the respective second and fifth semiconductor layers facing towardsthe substrate.
 18. The method of claim 17, wherein a cross-section ofthe second semiconductor layer taken along a direction that issubstantially parallel to the surface of the substrate and parallel tothe first and second gate structures has a first shape comprising uppersidewall surfaces defining an angle with respect to the surface of thesubstrate and facing away from the substrate and lower sidewall surfacesdefining an angle with respect to the surface of the substrate andfacing towards the surface of the substrate, wherein the thirdsemiconductor layer is on the upper sidewall surfaces of the secondsemiconductor layer, wherein a cross-section of the fifth semiconductorlayer taken along the direction has a shape comprising a plurality ofsecond shapes that are connected to each other in the direction, thesecond shapes being on respective ones of the second active fins andcomprising upper sidewall surfaces defining an angle with respect to thesurface of the substrate and facing away from the substrate, lowersidewall surfaces defining an angle with respect to the surface of thesubstrate and facing towards the surface of the substrate, and a topsurface that is parallel to the surface of the substrate, and whereinthe sixth semiconductor layer is on the upper sidewall surfaces of thefifth semiconductor layer.
 19. The method of claim 18, wherein a topsurface of the sixth semiconductor layer is substantially flat andsubstantially parallel to the surface of the substrate.
 20. A method ofmanufacturing a semiconductor device, the method comprising: forming anisolation pattern on a surface of a substrate, the isolation pattern onlower portions of a first active fin, a plurality of second active fins,and a plurality of third active fins, the substrate comprising first,second and third regions, wherein the first active fin, the plurality ofsecond active fins, and the plurality of third active fins are in thefirst, second, and third active regions, respectively; forming first,second and third dummy gate structures on the first to third activefins, respectively; forming first, second and third source/drain layerstructures, by a selective epitaxial growth (SEG) process, on portionsof the first to third active fins that are adjacent the first to thirdgate structures, respectively, the second source/drain layer structurecommonly contacting upper surfaces of the second active fins, and thethird source/drain layer structure commonly contacting upper surfaces ofthe third active fins; replacing the first to third dummy gatestructures with first, second and third gate structures, respectively;and forming first, second and third contact plugs on the first to thirdsource/drain layer structures, respectively, wherein a bottom of atleast one of the second and third contact plugs is substantially flatand substantially parallel to the surface of the substrate.